UNIVERSITY  OF  CALIFORNIA 

ANDREW 

SMITH 

HALL1DIR 


r    f 


HANDBOOK  ON  ENGINEERING. 


THE    PRACTICAL    CARE    AND    MANAGEMENT 


OF 


DYNAMOS,  MOTORS,  BOILERS,  ENGINES,  PUMPS,  1NSPIRA 

TORS  AND  INJECTORS,  REFRIGERATING  MACHINERY, 

HYDRAULIC  ELEVATORS,  ELECTRIC  ELEVATORS, 

AIR  COMPRESSORS,  ROPE  TRANSMISSION  AND 

ALL  BRANCHES  OF  STEAM  ENGINEERING. 


BY 

HENRY  C.  TULLEY, 

Engineer  and  Member  Board  of  Engineers,  St.   Louis. 


THIRD  EDITION.     lUO'J. 

and  Enlarged. 


//^         Of 


SOLD  BY 

HENRY  C.  TULLEY  &  CO., 

Wainwright  Building,  St.  Louis,  Mo. 

PRICE,  $3.50. 


HALLIDIE 


Entered  according  to  Act  of  Congress,  in  the  year  1900,  by 

HENRY  C.  TULLE  Y, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


Copyrighted,  1902. 


NIXON-JONES  PRINTING  Co 

215  PINB  STREET, 

ST.  Louis. 


INTRODUCTION. 

The  object  of  the  writer  in  preparing  this  work  has  been  to 
present  to  the  practical  engineer  a  book  to  which  he  can,  with 
confidence,  refer  to  for  information  regarding  every  branch  of 
his  profession. 

Up  to  the  date  of  the  publication  of  this  book,  it  was  impossi- 
ble to  find  a  plain  and  practical  treatise  on  the  steam  boiler,  steam 
pump,  steam  engine,  and  dynamo,  and  how  to  care  for  them; 
electric  and  hydraulic  elevators,  and  how  to  care  for  them  ;  and 
all  other  work  that  an  engineer  is  apt  to  come  in  contact  with  in 
his  profession. 

An  experience  of  over  twenty-five  years  with  all  kinds  of  en- 
gines and  boilers,  pumps,  and  all  other  kinds  of  machinery,  ena- 
bles the  writer  to  fully  understand  the  kind  of  information  most 
needed  by  men  having  charge  of  steam  engines  of  every  descrip- 
tion, and  what  they  should  comprehend  and  employ. 

With  this  object  in  view,  the  writer  has  carefully  made  note  of 
his  past  experience,  and  has  also  made  note  of  things  that  came 
to  his  notice  while  visiting  different  engine  rooms,  and  accord- 
ingly, has  taken  up  each  subject  singly,  excluding  therefrom, 
everything  not  strictly  connected  with  steam  engineering. 

Particular  attention  has  been  given  to  the  latest  improvements 
in  all  classes  of  steam  engineering  and  their  proportioning,  ac- 
cording to  the  best  modern  practice,  which,  it  is  hoped,  will  be 
of  great  value  to  engineers,  as  nothing  of  the  kind  has  heretofore 
been  published. 

This  book  also  contains  ample  instructions  for  setting  up,  lining, 
reversing  and  setting  the  valves  of  all  classes  of  engines. 

116603  THE  AUTHOR. 

(iii) 


CONTENTS. 


For  Alphabetical  Index  to  Subjects,  see  page  893. 


CHAPTER  I. 

PAGE. 

THE     ELEMENTARY     PRINCIPLES     OF     ELECTRICAL     MA- 
CHINERY             1 

A  permanent  magnet ; 1  to  2 

Two-bar  magnet 3  to  6 

A  magnet  needle 3 

Magnetic  lines  of  force     ......          ....->....       6 

Lines  of  force 6  to  14 

Magnetic  force 13 

To  find  the  lifting  capacity  of  a  magnet 13 

CHAPTER  II. 

THE  PRINCIPLES  OF  ELECTROMAGNETIC  INDUCTION    14  to  22 
The  armature  cores • 23  to  27 

CHAPTER  III. 

TWO-POLE  GENERATORS  AND  MOTORS 27 

The  simplest  type  of  armature  winding 27  to  29 

Two-pole  genera  tors  and  motors 27  to  30 

The  g  neral  arrangement  of  the  field  and  armature  in  a  two-pole 

machine  33  to  36 

The  reason  why  brushes  are  set  differently  on  motors  than  on 

dynamos 30  to  37 

V 


VI  CONTENTS. 

CHAPTER  IV. 

PAGE. 

MULTIPOLAR  MACHINES 38 

Multipolar  machines as  to  39 

Setting  the  brushes  on  a  four-pole  machine 40 

Setting  the  brushes  on  an  eight-pole  machine 41 

The  lap  and  wave  winding  for  four-pole  machine 42  to  40 

CHAPTER  V. 

SWITCH    BOARD,  DISTRIBUTING    CIRCUITS,  AND  SWITCH 

BOARD  INSTRUMENTS 47 

Generators  of  the  constant  potential       . 47  to  48 

The     switch-board     arranged     for     two   generators   of    the    shunt 

type 49  to  51 

Switch-board  for  three-wire  system 5G  to  57 

To  wire  a  large  building  with  a  lighting  and  power  system        .    58  to  60 

The  ammeters GO 

Circuit  breakers        ..." .    C>2  to  63 

The  electromotive  in  volts  force,  etc 63 

CHAPTER  VI. 

ELECTRIC  MOTORS 64 

Motors  and  their  connections 64  to  73 

The  strength  of  an  electric  current,  etc 73 

The  watt 73 

The  ampere 73 

Candle  power 73 

CHAPTER  VII. 

INSTRUCTIONS  FOR  INSTALLING  AND  OPERATING  SLOW 

AND  MODERATE  SPEED  GENERATORS  AND  MOTORS     .     .  74 

To  remove  the  armature       74 

Assembling  the  parts ....  74 

Filling  the  bearings 74 

To  complete  the  assembly 74 

Starting 74 

Care  of  commutator 75 


CONTENTS.  Vll 

PAGE. 

If  commutator  gives  trouble , 76 

General  directions  for  starting  dynamos     .     .     .     , 76,  77 

Bringing  dynamos  to  full  speed 77 

Connecting  one  dynamo  with  another 78 

Switching  dynamos  into  circuit 78 

How  dynamos  may  be  connected  together .     .     78 

Dynamos  in  parallel 79 

'Directions  for  running  dynamos  and  motors 80 

Precautions  in  running  dynamos 81 

Personal  safety 81 

CHAPTER  VIII. 

WHY  COMMUTATOR  BRUSHES  SPARK  AND'  WHY  THEY  DO 

NOT  SPARK 82  to  84 

The  way  in  which  the  current  is  shifted,  etc 84,  85 

Diagram  illustrating  the  same 85 

If  the  commutated  coil,  etc. 86 

Even  when  the  machine  is  properly  proportioned,  etc 87 

Sparking 87  to  91 

Noise 91  to  92 

Heating  in  dynamo  or  motor .    93  to  94 

The  effect  of  the  displacement  of  the  armature 94  to  98 

Table  of  carrying  capacity  of  wires 99,  101 

Insulation  resistance ....  100 

Soldering  fluid .101 

Table  showing  the  size  of  wire  of  different  metals  that  will  be  melted 
by  currents  of  various  strengths     .          102 

CHAPTER  IX. 

INSTRUCTIONS    FOR    INSTALLING  AND  OPERATING  APPA- 
RATUS FOR  ARC  LIGHTING,  BRUSH  SYSTEM 103 

Theory  of  the  Brush  arc  generator 103 

Bipolar  Brush  arc  generators 105 

General  data  on  bipolar  Brush  arc  generators 10(5 

Connections  of  No.  7£  and  No.  8  bipolar  generators 107 

Automatic  regulator  for  bipolar  Brush  arch  generators     .     .     .     .     .108 
Multipolar  Brush  arc  generators 11U 


Vlll  CONTENTS. 

PAGE. 

General  data  on  multipolar  Brush  arc  generate  •* Ill 

Method  of  suspending  armature Ill 

Method  of  handling  the  magnet  yoke 112 

Setting  the  brushes 112 

Care  of  commutator 114 

Connections  of  multipolar  Brush  arc  generators 114 

Connections  of  Nos.  8£,  9,  10  and  11  Brush  arc  generators,  single 

circuit,  clockwise  rotation  with  form  1  regulator 115 

Form  1  regulator  for  multipolar  Brush  arc  generators ll(> 

Connections  of  Brush  controller • 118 

Starting  the  multipolar  Brush  arc  generator  with  form  1  regulator  .  120 

Form  2  regulator  for  multipolar  Brush  arc  generators 120 

Adjustment  of  form  2  regulator 123 

Starting  the  multipolar  Brush  arc  generator  with  form  2  regulator  .  123 

Form  3  regulator  for  multipolar  Brush  arc  generators 124 

Form  4  regulator  for  multipolar  Brush  arc  generators 125 

Ammeter 125 

Instructions  for  installing  and  operating  improved  Brush  arc  lamps  .  125 

Connections  for  improved  Brush  arc  lamps 128 

Diagram  of  same  ..." 128 

Personal  safety 129 

Table  showing  relative  resistance  of  metals  at  temperature  of  70 

degrees  F 130 

View  of  tlie  Thomson-Houston  Standard  Arc  dynamo  arranged  for 

right-hand  rotation 131 


CHAPTER  X. 

INSTALLATION  OF  ARC  DYNAMOS 131 

Diagram  of  connections  for  arc  lighting  system       133 

Diagram  of  connections  for  rheostat .134 

View  of  controller  for  arc  dynamos 135 

Testing  arc  light  dynamos 137 

Diagram  showing  commutator  segments  and  brush  holders,  etc.    .     .  138 

Table  of  leads 140 

Diagrams  showing  best  position   of  air  blasts  and  jets  on  L  1)  and 

M  D  dynamos 141 

Directions  for  setting  the  air  blast,  etc .  142 


CONTENTS.  ix 

PAGE. 

Some  troubles   which  may  be  met  and  their  causes  —  reversal  of 

polarity 142 

Ring  armatures 144 

Standard  plug  switchboard  for  6  circuits 147 

Switchboards       147 

View  of  the  back  of  switchboard 148 

View  of  meter  for  station  use 149 

Connections  for  watt  meters  for  series  arc  circuits 149 

Watt  meters 150,  151 

Instructions  for  the  installation  and  care  of  arc  lamps 151 

View  of  interior  of  M  arc  lamp 150 

Starting  the  lamps 152 

Diagram  of  connections  for  M  and  K  arc  lamps 152 

Instructions  for  repairing,  testing  and  adjusting  arc  lights  ....  153 
Table  of   magnetizing  force   in  ampere   turns  required  per  inch  of 
length  of  magnetic  circuit 159 

CHAPTER  Xa. 

INCANDESCENT  WIRING  TABLES  160  to  168 

Amperes  per  motor  table 169,170 

Volts  lost  at  different  per  cent  drop 171,172 

Amperes  per  lamp  table 173 

Approximate  weight  of  "  O.  K."  triple  braided  weatherproof  copper 

wire  . 174 

Table  showing  difference  between  wire  gauges  in  decimal  parts  of  an 

inch 175 

Electric  light  conductors  table 176 

CHAPTER  XI. 

THE  STEAM  ENGINE 177 

The  selection  of  an  engine 177 

The  gain  by  expansion 183 

Table  of  cut-off  in  parts  of  the  stroke 183 

The  steam  engine  governor 183  and  194 

The  fly-wheel 184 

Horse  power 185 

Care  and  management  of  a  steam  engine 185 


X  CONTENTS. 

PAGE. 

Lubrication  of  an  engine 18(> 

Selecting  an  oil  for  an  engine 187 

The  piston  packing 187 

Crank-pins 188 

Connecting  rod  brasses 189 

Knocking  in  engines 189  to  190 

The  main  bearings 190  to  192 

Repairs  of  engines 191 

Fitting  a  slide  valve 191 

Eccentric  straps 192 

Heating  of  journals 193 

Automatic  engines 194 

To  find  the  dead  centers  .     .     .     .     • 195 

View  of  tandem  compound  engine  and  its  foundation 198 

How  to  line  an  engine 199  to  203 

View  of  twin  tandem  compound  engine^    showing   arrangement   of 

•   piping 200 

CHAPTER  XIa. 

Directions  for  setting  up;  adjusting  and  running  the  improved  Cor- 
liss steam  engene 205 

Adjustment  of  Corliss  valve  gear  with  single  and  double  eccentrics.  206 

Adjustment  with  two  eccentrics     .     • .     .215 

The  compound  engine 222 

Horse  power  of  compound  engine 232 

Condensing  engines 232 

Condensers 235 

Setting  the  piston  type  of  valve 238 

Setting  the  cut-off  valve 243 

Flat  valve  riding  cut- off 245 

CHAPTER  XII. 

THE  STEAM  ENGINE  —  CONTINUED        • .     .  251 

What  is  work 251 

What  is  power 251 

Horse  power  of  an  engine 252 

General  proportions  of  engine . 252 


CONTENTS.  XI 

PAGE. 

Rules  for  weights  of  fly-wheels 253 

View  of  the  Russell  engine  254 

Setting  the  valves  of  Russell  engines 254 

View  of  the  Porter- Allen  engine 258 

Description  of  the  Porter-Allen  engine 259,271 

Directions  for  setting  the  valves,  and  running  the  Porter-Allen 

engine 271,  273 

Specifications  for  centrally  balanced  Centrifugal  Inertia  Governor  273,  275 

The  Armington  and  Sims  engine 275 

Setting  the  valve  in  an  Armington  and  Sims  engine 275 

The  Harrisburg  engine 276 

The  care  and  management  of  the  Harrisburg  engine  ....  276-281 

The  Mclntosh  and  Seymour  High  Speed  engine  281 

How  to  set  the  valves  of  an  M.  and  S.  engine  . 281 

The  Ideal  engine 283 

Instructions  for  starting  and  operating  Ideal  engines  ....  283,  291 

Instructions  for  indicating  Ideal  engines 291,  292 

The  Westinghouse  Compound  engine 293 

Instructions  for  starting  and  operating  a  Westinghouse  Compound 

engine 292,  309 

How  to  set  the  main  valve  on  a  Westinghouse  engine .301 

How  to  rebabbitt  connecting  rods  305 

Some  points  on  cylinder  lubrication 309 

Automatic  lubricators  310,  312 

Setting  a  plain  slide  valve  with  link  motion 313,318 

Valve  setting  for  engineers 318,  322 

View  of  a  slide  valve  engine  showing  the  point  of  taking  steam  .  .321 
View  of  a  slide  valve  engine  showing  the  point  of  cut-off  .  .  .  .321 
View  showing  the  position  of  the  valve  when  compression 

begins 321,  322 

CHAPTER  XIII. 

TAKING  CHARGE  OF  A  STEAM  POWER  PLANT 323 

Economy  in  steam  power  plants 327,  329 

Priming  in  boilers 329 

Table  of  properties  of  saturated  steam 330 

High  pressure  steam 332,  335 

Using  steam  full  stroke 335,337 


XIV  CONTENTS . 

1'AGE. 

Zigzag  riveting  and  chain  riveting 4(58,  472 

Single  riveted  lap  joints,  iron  plates 469 

Steel  plates  and  steel  rivets,  S.  R.  L.  J 470 

Steel  plates  and  steel  rivets,  D.  R.  L.  J 471 

Strength  of  stayed  flat  boiler  surfaces 473 

Boiler  stays 474,  477 

Riveted  and  lap  welded  flues 477,  481 

Table  of  allowable  steam  pressure  on  flues 478,  479 

Thickness  of  material  required  for  tubes 481,486 

Table  of  wrought-iron  welded  pipe 486 

Pulsation  in  steam  boilers 487,  488 

Weight  of  square  and  round  iron  per  lineal  foot 488 

Water  columns  for  boilers     .     , 489 

Steam  gauges 489,  490 

Safety  valves 491,  499 

Table  of  the  rise  of  safety  valves 494 

Safety  valve  rules 497 

Table  of  heating  surfaces  in  square  feet 501 

Centrifugal  force 501 


CHAPTER  XVIII, ' 

THE  WATER  TUBE  SECTIONAL  BOILER 502 

The  down  draft  furnace 503,  522 

View  of  boiler  setting  and  furnace  common  in  the  East 513 

Vertical  tubular  boilers     .     . 514,  521 

Proper  water  column  connections 515 

Table  of  pressures  allowable  in  boilers 516 

Eire  line  in  boiler  settings 520 

Proper  location  of  gauge  cocks 521 

Number  of  bricks  required  for  boiler  setting  ...          522 

Specifications  for  a  sixty-inch  6-inch  flue  boiler  ........  524 

Banking  flres 531 

Instructions  for  boiler  attendants 532 

Rules  and  problems  anent  steam  boilers 536 

Steam  jets  for  smoke  prevention 542 


CONTENTS.  XV 

CHAPTER  XIX. 

PAGE. 

THE  STEAM  PUMP ....  544 

The  Worthington  Compound  pump 544 

View  of  steam  valves  properly  set 545 

The  Deaue  steam  pump 546 

View  of  steam  valves  properly  set 547 

The  Cameron  steam  pump 548 

Explanation  of  steam  end 548 

View  of  steam  valves  properly  set 548 

The  Knowles  steam  pump 550 

Explanation  of  steam  valves 550 

View  of  steam  valves  properly  set 552 

The  Hooker  steam  pump 553 

Operation  of  the  Hooker  pump 553 

View  of  steam  valves  property  set 555 

The  Blake  steam  pump 555 

Operation  of  the  Blake  pump 556 

View  of  steam  valves  properly  set 558 

Miscellaneous  pump  questions  and  answers     .     .     .     ...     .  559  and  G03 

How  to  set  the  steam  valves  of  a  duplex  pump .  567 

View  of  steam  valves  properly  set 568 

Proper  pipe  connections 569 

View  of  pipe  connections 570 

Pumps  refusing  to  lift  water      . »     .     .     .     .  577 

Corrosion  in  water  pipes 579 

Pumping  acids 579 

Selecting  boiler  for  a  steam  pump 580 

The  Worthington  water  meter 581 

Table  of  water  pressure  due  to  height 582 

Table  of  decimal  equivalents  of  IGths,  32n.ds  and  64ths  of  an  inch      .  583 

Capacity  of  tanks  in  U.  S.  gallons .  584 

Capacity  of  square  cisterns  in  U.  S.  gallons    .     .     .     .     .     .     .     .   ".  585 

Weight  of  water 585 

Cost  of  water 587 

Loss  by  friction  of  water  in  pipes 588 

How  water  may  be  wasted 589 

Ignition  points  of  various  substances 589 


XV1U  .  CONTENTS. 

PAGE. 

Pure  water 681 

The  temperature  and  pressure  of  saturated  steam 684 

Something  for  nothing •     .  686 

Melting  point  of  metals 687 

Chimneys 688  to  694 

Weight  of  steel  smoke  stacks  per  linear  foot 694 

CHAPTER  XXIV. 

HORSE  POWER  OF  GEARS 695 

Table  of  H.  P.  of  shafts 697 

Prime  movers 697 

Wheel  gearing     . 698 

The  pitch  line  of  a  gear  wheel 698 

To  find  the  pitch  of  a  wheel 698 

To  find  the  chordal  pitch 699  to  703 

To  find  the  diameter  of  a  wheel 699  to  703 

To  find  the  number  of  teeth  for  a  wheel "699  to  703 

To  find  the  proportional  radius  of  a  wheel  or  pinion 700 

To  find  the  diameter  of  a  pinion 700 

To  find  the  circumference  of  a  wheel 700 

To  find  the  number  of  revolutions  of  a  wheel  or  pinion     .     .     700  to  70 1 

Stress  on  gear  teeth 705 

A  train  of  wheels  and  pinions 701 

Table  of  diameters  and  pitches  of  wheels 701 

Curves  of  teeth 705 

Construction  of  gearing 706 

Bevel  wheels 707 

Worm-screw ' ......  708 

Proportions  of  teeth  of  wheels 709 

To  find  the  depth  of  a  cast-iron  tooth 709 

To  find  the  horse-power  of  a  tooth 710 

Calculating  the  speed  of  gears 710 

When  time  must  be  regarded 711 

Table  of  weight  of  a  square  foot  of  sheet  iron    .     . 712 

Screw  cutting 713 

Transmission  of  power  by  manila  rope 714,812,813 

Decimal  equivalents  of  one  foot  by  inches 714 

Table  of  transmission  of  power  by  wire  ropes 715  and  8 14 


CONTENTS.  XIX 

CHAPTER  XXV. 

PAGE. 

ELECTRIC  ELEVATORS 716 

The  Otis  elevator 716 

Belt  driven  elevators 716,  725 

Direct  connected  elevators 717,  730 

The  motor-starting  switch 719 

The  elevator  machine  brake       720 

The  main  hand  rope 721 

View  of  connections  of  gravity  motor  controller  to  elevator     .     .     .  722 
View  of  connections  of  gravity  motor  controller  with  separate  rope 

attachment 723 

Direct  connected  electric  elevators 730 

Automatic  stops       733 

View  of  circuit  connections 734 

The  starting  resistance 735 

The  switch  lever 736 

Cutting  out  the  series  field  coils 737 

The  safety  brake  magnet 739 

The  proper  care  of  machines 739,  779 

How  to  start  the  car 74:3 

The  car  switch 748 

The  slack  cable  switch 749 

P^lectric  control  for  private  house  elevators 749 

View  of  wiring  for  private  houses 750 

The  Sprague  Electric  Co.'s  elevators 756 

View  of  operative  circuits  for  Sprague  screw  elevator     .     .     .     .     .  762 

The  pilot  motor " .763 

Care  of  Sprague  elevators 765 

Directions  for  the  care  and  operation  of  electric  elevators   ....  765 


CHAPTER  XXVI. 

HYDRAULIC  ELEVATORS 769 

How  to  pack  hydraulic  vertical  cylinder  elevators 769 

How  to  set  the  hand  cable  on  a  iever  machine 770 

How  to  pack  vertical  cylinder  valves 771 

View  of  Otis  vertical  hydraulic  elevator  and  valve   chamber,  and 
packing  same 772 


XX  CONTENTS. 

PAGE. 

View  of  the  Crane  auxiliary  and  main  valve,  and  operation  of  same     .  775 

Automatic  stop  valve 776 

Leather  cup  packings  for  valves 784 

Closing  down  elevators 784 

Otis  gravity  wedge  safety 777 

Care  of.  Hale  elevators 777 

Water  for  use  in  hydraulic  elevators 778,781 

Otis  differential  and  auxiliary  valve 780 

Elevator  inclosures  and  their  care 782 

Standard  hoisting  rope  with  19  wires  to  the  strand       783 

Cables,  and  how  to  care  for  them 783 

Lubrication  for  hydraulic  elevators 785 

Belts,  and  how  to  care  for  them 786 

Useful  information 786 

To  find  leaks  in  pressure  tanks 786 

Decimal  equivalents  of  an  inch 787 

CHAPTER  XXVII. 

THE  DRIVING  POWER  OF  BELTS 788 

The  average  strain  or  tension  at  which  belting  should  be  run     .     .     .  788 

Rules  and  problems  anent  belting       788,71)7 

Extracts  from  articles  on  belts,  by  It.  J.  Abernatliy 790 

Transmitting  power  of  belts 795 

Table  of  horse-power  of  belts 790,799 

Directions  for  adjusting  belting 798 

Horse  power  of  belting '. 799 

CHAPTER   XXVIII. 

AIR  COMPRESSORS,   THERMOMETERS,   THE   METRIC  SYS- 
TEM, AND  ROPE  TRANSMISSION 800 

Losses  in  air  compressors 800 

Capacity  of  air  compressors 800 

Contents  of  a  cylinder  in  cubic  feet  for  each  foot  in  length  ....  801 

The  McKierman  air  compressor 801 

The  Bennett  automatic  air  compressor 803 

The  Ingersoll-Sergeant  air  compressor .  803 

The  Pohle  air  lift  system .807 


CONTENTS .  XXI 

1'AGE, 

The  metric  system 80) 

Thermometers 811 

Rope  transmission .     .     812 

Horse-power  transmitted  by  hemp  ropes  ..     .     .     .     .     .     .     .     .     .813 

To  test  the  purity  of  hemp  ropes 814 

Wire  rope  data 814 

CHAPTER  XXIX. 

ALTERNATING  CURRENT  MACHINERY .815 

The  principles  of  alternating  currents 815 

Diagrams  representing  a  generator  of  either  continuous   or  alter- 
nating currents 817 

Diagrams   showing   the  relations  between   alternating  currents  and 

e.m.fs 821,825 

One  reason  why  alternating  currents  vary,  etc 825 

Diagrams  showing  the  way  in  which  sine  curves  are  used,  etc.      .     .  826 

Polyphase  currents '...." 832 

Unbalanced  three-phase  currents,  etc .•    .  834 

Inductive  action  in  alternating  current  circuits,  etc 834 

The  angle  of  lag  between  the  current,  etc 837 

By  the  use  of  condensers,  etc 840 

The  general  principle  of  construction  of  a  condenser,  etc.     ....  841 

Mutual  induction 842 

Transformers 844 

The  action  in  a  transformer 846 

The  object  in  using  transformers 849 

Alternating  current  generators      . 852 

Diagram  illustrating  a  simple  alternating  current  generator      .     .     .854 

Alternator  of  the  multipolar  type 855 

How  alternating  current  generators  are  run     . 859 

If  an  alternator  is  of  the  multipolar  type 854 

A  revolving  field  alternator 857 

An  inductor  alternator 858 

Alternating  current  generators 859 

Alternators  run  in  parallel 860 

Starting  alternators  connected  in  parallel 861 

The  way  in  which  synchronizing  lamps  are  connected 863 

Compensating  and  compounding  alternators    .     .     .     . "   .     .     .     .     .  864 


2  HANDBOOK    ON    ENGINEERING. 

also  upon  the  temper  it  is  given.  Generally  speaking,  the  harder 
the  steel  the  stronger  the  magnet.  A  bar  of  soft  steel,  or  wrought 
iron,  cannot  be  made  into  a  permanent  magnet  of  any  noticeable 
strength,  but  if  such  a  bar  is  covered  with  a  coil  of  wire,  as  shown 
in  Figs.  3  and  4,  and  a  current  of  electricity  is  passed  through 
the  wire,  the  bar  will  be  converted  into  a  very  strong  magnet  so 
long  as  the  current  flows.  As  soon  as  the  electric  current  stops 
flowing  through  the  wire,  the  magnetism  of  the  bar  will  die  out. 

Magnets  of  the  last-named  type  are  called  electro-magnets,  as 
they  do  not  possess  magnet  properties  except  when  the  electric 
current  flows  around  them.  Electro-magnets,  when  energized  by 
sufficiently  strong  electric  currents,  can  be  far  more  powerful  than 
the  permanent  magnets,  and  on  that  account  they  are  used  in 
electric  generators  and  motors.  In  addition  to  being  stronger 
magnets,  the  electro-magnet  has  the  advantage  that  it  can  be 
magnetized  and  demagnetized  almost  instantly,  by  simply  cutting 
off  the  exciting  electric  current,  and  on  this  account  they  can  be 
used  for  parts  of  electrical  machines  and  apparatus,  for  which  the 
permanent  magnet  would  be  entirely  unsuited. 

If  we  test  the  attractive  power  of  a  magnet,  we  will  find  that 
it  is  greatest  at  the  ends,  the  force  at  the  middle  point  being 
scarcely  noticeable.  A  bar  such  as  Fig.  1  or  Fig.  3  might  hold  a 
piece  of  iron  weighing  several  pounds,  if  presented  to  either  end, 
while  at  the  middle  point,  it  might  not  be  able  to  sustain  more 
than  an  ounce  or  two.  Owing  to  this  fact,  the  ends  are  called 
the  poles  of  the  magnet. 

If  any  magnet  is  suspended  from  its  center,  like  a  scale  beam, 
and  allowed  to  swing  freely,  it  will  be  found  that  it  will  come  to 
rest  in  a  north  and  south  position,  and  no  matter  how  violently  it 
may  be  moved  around,  it  will  always  come  to  a  state  of  rest 
with  the  same  end  pointing  towards  the  north.  On  this  ac- 
count, the  ends  are  called  north  and  south  poles,  the  north  pole 
being  the  end  that  points  toward  the  north. 


HANDBOOK    ON    ENGINEERING. 


3 


If  two-bar  magnets  are  suspended  side  by  side  with  the 
north  end  of  one  at  the  top  and  the  north  end  of  the  other 
at  the  bottom,  as  is  illustrated  in  Fig.  5,  they  will  attract  each 
other ;  but  if  both  magnets  had  the  north  end  at  the  top,  they 
will  push  away,  as  shown  in  Fig.  6.  It  is  evident  that  there  is 
a  good  reason  for  this  difference  in  action,  and  this  reason  we 
can  find  out  by  experiment. 


a 


a 


a 


Fig.  5. 


Fig.  6. 


A  magnet  needle,  such  as  is  used  in  mariner's  compasses,  is 
simply  a  small  magnet.  If  we  place  a  magnet  bar,  as  shown  in 
Fig.  7,  and  then  set  near  to  it,  in  different  positions,  a  compass 
containing  a  very  small  needle,  we  will  find  that  in  these  several 
positions  the  direction  of  the  needle  will  be  about  as  is  indicated 
by  the  small  arrows  marked  I)  on  the  curved  lines  a  a;  the  point 
of  the  arrow  being  the  north  end,  or  pole  of  the  needle.  The 
reason  why  the  needle  will  take  up  these  positions  is  that  the  north 
end  of  the  bar  attracts  the  south  end  of  the  needle,  and  pushes 
away  the  north  end,  just  as  in  Figs.  5  and  6,  and  the  south  end 
of  the  bar  acts  in  the  same  way ;  so  that  there  is  a  tug  of  war 
going  on,  so  to  speak,  between  the  attractions  and  repulsions  of 


4  HANDBOOK    OX    ENGINEERING. 

the  two  ends  of  the  bar  upon  the  two  ends  of  the  needle,  the 
result  being  that  the  position  assumed  by  the  needle  is  the  re- 
sultant of  these  several  actions.  When  the  needle  is  near  the 


\ 


V 


.s  v. 


Fig.  7. 


\ 


Fig.  8. 


north  pole  of  the  bar,  its  south  end  is  attracted  with  the  greatest 
force,  and  when  near  the  south  end  of  the  bar,  the  north  end  ex- 
periences the  greatest  attraction. 

If  we  were  to  place  the  exploring  needle  in  all  possible  posi- 
tions near  the  magnet  and  trace  lines  parallel  with  it,  in  these 
positions,  we  would  obtain  a  large  number  of  curves  about  the 
shape  of  those  shown  in  Fig.  8.  As  these  curves  represent  the 
direction  into  which  the  magnet  needle  is  turned  at  the  various 
points  in  the  vicinity  of  the  magnet,  they  represent  the  direction 
in  which  the  combined  forces  of  the  two  poles  act  at  these  two 
points,  hence,  these  lines  are  called  magnetic  lines  of  force. 


HANDBOOK    ON    ENGINEERING. 


When  two  magnets  are  suspended  as  in  Fig.  5,  the  lines  of 
force  of  both  will  be  in  the  same  direction  as  is  indicated  in  Fig. 
9  by  the  arrow  heads  on  the  curves  a  a.  That  this  is  true  can  be 
seen  from  Fig.  7,  in  which  it  will  be  seen  that  the  arrow  heads 
point  toward  the  south  pole  and  away  from  the  north  pole. 
As  the  north  pole  of  a  magnet  has  an  attraction  for  the  south 
pole,  we  can  readily  see  that  there  is  an  endwise  pull  in  the 
lines  of  force,  which  tends  to  make  them  contract,  like  rubber 
bands,  hence,  we  can  imagine  the  lines  a  a  in  Fig.  9  to  contract 
and  thus  draw  the  two  magnet  bars  together. 

The  repulsion  of  the  two  magnets,  when  the  north  poles  are  at 
the  same  end,  is  illustrated  in  Fig.  10.  Here  we  see  that  the  lines 
of  force  passing  on  the  outside  of  the  bars,  as  indicated  by 
lines  a  a,  are  unobstructed,  and  can  assume  their  natural  posi- 


a 


JV 


s 


Fig.  9. 


Fig.  10. 


tion,  but  those  that  pass  between  the  bars,  along  line  c,  are 
pressed  out  of  position.  If  we  assume  that  the  lines  of  force 
make  an  effort  to  retain  their  position,  like  so  many  wire 


6  HANDBOOK    ON    ENGINEERING. 

springs,  then  we  can  see  that  the  repulsion  is  due  to  the  effort  that 
the  lines  make  to  assume  their  natural  form  in  the  space  between 
the  bars. 

Magnetic  lines  of  force  have  no  real  existence,  they  simply  in- 
dicate the  direction  in  which  the  force  acts,  but  if  we  keep  this 
fact  in  mind,  it  helps  us  to  understand  magnetic  actions,  if  we 
treat  the  lines  of  force  as  if  they  were  something  real.  This  fact 
will  become  more  evident  as  we  proceed. 

Lines  of  force  always  pass  from  the  north  to  the  south  pole 
through  the  space  between  these  poles,  and  through  the  magnet 
itself,  they  are  assumed  to  pass  from  the  south  to  the  north  pole. 
The  form  of  the  lines  of  force  depends  upon  the  relative  position 
of  the  north  and  south  poles.  In  Fig.  9  they  are  curved,  as 

a 


s                     w 

E==E 

S                              jy 

Fig.  11. 

the  magnets  are  placed  side  by  side,  but  if  the  bars  were  arranged 
end  to  end,  as  in  Fig.  11,  the  lines  of  force  would  be  straight,  as 
is  shown  at  a.  From  the  north  end  of  the  right  side  magnet,  the 
lines  of  force  would  pass  in  curved  line,  as  in  Fig.  10,  to  the  south 
pole  of  the  magnet  on  the  left  side,  thus  completing  the  magnetic 
chain,  or  circuit,  as  it  is  called. 

If  we  take  the  two  magnet  bars  of  Fig.  11  and  stand  them  on 
end,  as  in  Fig.  12,  and  suspend  a  bent  wire  C  in  the  manner 
shown,  effects  can  be  produced  that  are  interesting  and  instruct- 
ive, as  they  illustrate  the  principle  upon  which  generators  and 
motors  act.  The  wire  0  should  be  journaled  at  D  D,  so  as  to 
swing  with  as  little  friction  as  possible,  and  its  ends  are  to  be  con- 
nected with  a  battery  J5,  by  means  of  fine  wires  a  and  b;  a  switch 
being  provided  at  c  so  as  to  stop  the  flow  of  current  when  desired. 


HANDBOOK    ON    ENGINEERING.  7 

I*  the  switch  c  is  opened,  so  that  no  current  flows  through  C,  the 
latter  will  not  be  disturbed,  and  if  we  give  it  a  swing,  it  will  oscil- 
late back  and  forth,  like  a  clock  pendulum,  and  in  a  few  seconds 
come  to  rest  in  the  position  in  which  it  is  shown.  If  the  switch 
is  closed,  C  will  at  once  swing  out  of  the  stream  of  magnetic  lines 
of  force  and  will  remain  in  that  position  as  long  as  the  current 
from  the  battery  passes  through  it.  The  direction  in  which  C 


Fig.  12. 

will  swing  will  depend  upon  the  direction  of  the  current  through 
it.  If  with  the  wires  a  and  6  connected  with  the  battery,  in  the 
manner  shown,  the  wire  C  swings  to  the  right  side,  then  if  a  is 
connected  with  e,  and  b  with  d,  the  direction  of  swing  will  be 
reversed  ;  that  is,  C  will  swing  toward  the  left. 

From  this  experiment  we  see  that  the  magnetic  lines  of  force 
can  develop  a  repulsive  force  against  an  electric  current,  and  that 
the  direction  of  the  repulsion  depends  upon  the  direction  of  the 


8 


HANDBOOK    ON    ENGINEERING. 


electric  current  with  respect  to  the  direction  of  the  lines  of  force. 
We  now  desire  to  know  why  this  repulsion  is  developed,  and  this 
we  can  ascertain  by  the  following  experiments :  — 

If  we  arrange  three  wires  as  shown  in  Figs.  13,  14  and  15,  so 
as  to  run  north  and  south,  the  upper  end  being  north,  and  place 
over  these  magnet  needles  D  D  D,  pivoted  at  e  e  e,  we  will  find 
that  if  there  is  no  current  flowing  through  the  wire,  the  needle 
will  point  toward  the  north,  or  be  parallel  with  the  wire,  as  is 


Fig.  13. 


Fig.  14. 


Fig.  15. 


shown  in  Fig.  14.  If  the  current  runs  through  the  wire  from 
south  to  north,  the  north  end  of  the  needle  will  swing  to  the  right, 
as  in  Fig.  15,  and  if  the  current  runs  through  the  wire  from  north 
to  south,  the  north  end  of  the  needle  will  swing  toward  the  left, 
as  in  Fig.  13.  From  this  we  see  that  an  electric  current  can 
repel  a  magnet,  and  that  the  direction  in  which  it  repels  it  depends 
upon  the  direction  of  the  current. 

If  we  stand  the  three  wires  on  end,  as  shown  in  Figs.  16,  17 
and  18,  in  which  ABC  represent  the  wires  as  seen  from  above, 
we  will  find  out  more  about  the  relation  between  electric  currents 


HANDBOOK    ON    ENGINEERING. 


and  magnets.  If  we  place  four  small  magnet  needles  around  each 
one  of  the  wires,  as  shown  at  a  a  a  a,  we  will  find  that  those 
around  the  center  wire,  through  which  no  current  flows,  will  all 

a 


Fig.  16. 


Fig.  18. 


point  toward  the  north,  as  shown,  while  those  around  the  wire 
Fig.  16,  through  which  a  current  flows  upward,  that  is,  away  from 
the  center  of  the  earth,  will  point  in  a  direction  opposite  to  that 
in  which  the  hands  of  a  clock  move;  and  in  wire  Fig.  18,  in 
which  the  electric  current  flows  down  toward  the  center  of  the 
earth,  the  north  ends  of  all  the  needles  will  point  in  the  direction 
in  which  the  hands  of  a  clock  move,  that  is,  just  opposite  to  those 
in  Fig.  16. 


.(IP 


Fig.  19. 


Fig.  20. 


From  these  actions,  we  infer  at  once  that  when  an  electric 
current  flows  through  a  wire,  the  latter  becomes  surrounded 
with  magnetic  lines  of  force,  as  is  illustrated  in  Figs.  19  and  20, 


10  HANDBOOK    ON    ENGINEERING. 

and  that  there  is  a  fixed  relation  between  the  direction  of  the 
current  and  that  of  the  lines  of  force.  At  A,  Fig.  19,  the  direc- 
tion of  the  lines  of  force  is  shown  for  a  current  moving  up- 
ward, and  at  B,  Fig.  20,  the  direction  of  the  lines  of  force  is 
that  due  to  a  current  moving  downward  through  the  wire. 

Inasmuch  as  an  electric  current  flowing  through  a  wire  is 
surrounded  by  magnetic  lines  of  force,  we  can  say  that  a  com- 
plete electric  current  consists  of  two  parts,  one  the  current  proper, 
which  traverses  the  wire,  and  the  other  the  magnetic  casing  which 
envelops  the  wire.  It  is  the  action  between  the  latter  part  of  the 
current  and  the  lines  of  force  of  magnets  that  develops  the 
current  in  a  generator,  or  the  power  in  a  motor. 

With  the  aid  of  Figs.  21  and  22,  we  can  now  show  how  the 
force  is  developed  that  thrusts  the  wire  to  one  side  in  Fig.  12. 
The  lines  of  force  of  the  magnet,  which  constitute  what  is  called 
the  magnetic  field,  will  flow  from  the  north  pole  at  the  top  to  the 
south  pole  at  the  bottom,  as  is  shown  in  Figs.  21  and  22.  If  the 
electric  current  flows  through  the  wire  C  from  the  back  toward 
the  front,  the  lines  of  force  developed  around  it  will  have  the 
direction  shown  in  Fig.  21.  As  lines  of  force  cannot  flow  in  op- 
posite directions  in  the  same  space,  the  lines  of  the  field  will  swing 
over  to  the  left  side  of  the  wire,  but  in  doing  so  they  will  be 
stretched  out  of  the  straight  form,  and  they  will  also  push  the 
lines  surrounding  the  wire  out  of  their  central  position.  Under 
these  conditions,  which  are  illustrated  in  Fig.  21,  the  effort  made 
by  the  field  lines  to  straighten  out,  together  with  the  effort  made 
by  the  wire  lines  to  return  to  the  central  position,  will  develop  a 
thrust  between  the  wire  and  the  field,  and  thus  force  the  former 
out  toward  the  right  side. 

If  the  direction  of  the  current  through  the  wire  is  reversed  so 
as  to  flow  from  front  to  back,  the  direction  of  the  lines  of  force 
around  the  wire  will  be  reversed,  and  will  be  as  in  Fig.  22.  Under 
these  conditions,  the  lines  of  force  of  the  magnetic  field  will 


HANDBOOK    ON    ENGINEERING. 


11 


swing  over  to  the  right  side  of  the  wire,  and  thus  the  thrust  will 
be  in  the  opposite  direction. 

Fig*  J2  represents  the  principle  of  an  electric  motor  in  its  sim- 
plest form,  and  from  it  we  see  that  the  force  that  causes  the 
armature  to  rotate  is  developed  by  the  repulsion  between  the  mag- 
netism of  the  field  magnet  and  the  magnetism  that  surrounds  the 
wires  wound  upon  the  armature. 


Fig.  21. 


Fig.  22. 


It  is  self-evident  that  if  we  undertake  to  force  the  wire  C 
through  the  magnetic  field  in  the  opposite  direction  to  that  in 
which  it  swings,  we  will  have  to  make  an  effort  to  do  so ;  that  is, 
if  we  try  to  move  the  wire  from  right  to  left  in  Fig.  21,  or  from 
left  to  right  in  Fig.  22.  we  will  have  to  apply  power.  Now  nature 
is  a  strict  accountant  and  does  not  allow  any  power  to  be  lost ; 
therefore,  all  the  energy  we  expend  in  moving  the  wire  through 
the  magnetic  field  must  appear  in  some  other  form,  and  the  form 
in  which  it  appears  is  as  an  electric  current  that  is  generated  in 


12  HANDBOOK    ON    ENGINEERING. 

the  wire.  If  we  were  to  remove  the  battery  in  Fig.  12  and  put 
in  its  place  an  instrument  to  indicate  the  presence  of  a  current  in 
the  wire,  we  would  find  that  >Vhen  we  move  the  latter  in  the 
opposite  direction  to  that  in  which  it  moves  under  the  influence  of 
the  current,  we  generate  a  current;  that  is,  we  convert  the  device 
into  a  simple  electric  generator.  If  in  Fig.  21,  we  move  the  wire 
from  right  to  left,  the  direction  of  the  current  generated  in  the 
wire  will  be  the  same  as  that  of  the  current  which  causes  the  wire 
to  swing  in  the  opposite  direction,  that  is,  from  back  toward  the 
front.  As  it  is  a  poor  rule  that  does  not  work  both  ways,  we 
would  naturally  infer  that  if  moving  the  wire  from  right  to  left 
develops  a  current  from  back  to  front,  movement  in  the  opposite 
direction  would  develop  a  current  from  front  to  back ;  and  such 
is  actually  the  case.  This  fact  can  be  demonstrated  by  Fig.  12. 
Suppose  that  in  this  figure  we  hold  C  stationary  in  the  central 
position,  and  then  pass  a  current  through  from  back  toward  the 
front ;  this  current  would  exert  a  force  to  swing  C  to  the  right 
side.  If  we  release  the  wire,  it  will  swing  to  the  right  and  as 
soon  as  it  begins  to  move,  the  current  will  become  weaker,  show- 
ing that  the  movement  of  the  wire  developed  therein  a  current  in 
the  opposite  direction.  If  we  force  the  wire  over  to  the  left  side, 
the  current  flowing  through  it  will  begin  to  increase  as  soon  as 
the  wire  moves. 

All  the  foregoing  shows  us  that  when  a  wire  is  moved  through 
a  magnetic  field,  a  current  will  be  generated  in  it  if  it  forms  part 
of  a  closed  circuit,  and  it  makes  no  difference  whether  there  is  a 
current  already  flowing  in  the  wire  or  not.  When  the  wire  is 
caused  to  move  through  the  magnetic  field  by  a  current  flowing 
through  it  from  an  external  source,  the  current  developed  in  it  will 
be  in  opposition  to  that  which  comes  from  the  external  source, 
and,  as  a  consequence,  the  movement  produces  an  actual  reduc- 
tion of  the  strength  of  current  flowing  through  the  wire.  The 
stronger  the  magnetic  field  and  the  greater  the  velocity  of  the 


HANDBOOK    ON    ENGINEERING.  13 

wire,  the  stronger  the  current  generated  in  opposition  to  the  driv- 
ing current,  and,  therefore,  the  weaker  the  latter.  It  is  on  this 
account  that  if  a  motor  is  allowed  to  run  free,  the  faster  it  runs 
the  weaker  the  current  through  it  becomes,  as  the  actual  current 
in  every  case  can  only  be  the  difference  between  the  main  driving 
current  and  the  one  developed  in  the  wire,  which  latter  runs  in 
the  opposite  direction. 

Magnetic  force  is  measured  in  units  that  are  based  upon  the 
centimeter  grame  second  system  which  is  too  technical  to  be  ex- 
plained in  a  few  words.  Briefly  stated  a  unit  of  magnetic  force 
will  exert  a  pull  of  unit  mechanical  force  at  a  unit  distance. 

The  force  of  magnets  is  measured  either  by  the  total  force  of 
the  magnet,  or  by  the  force  exerted  by  each  unit  of  cross-section. 
When  the  measurement  is  based  upon  the  total  force  of  the  mag- 
net, the  unit  is  called  a  Maxwell ;  thus  we  speak  of  the  total  flux 
of  a  magnet  as  so  many  maxwells.  When  the  measurement  is 
referred  to  the  force  per  unit  of  cross-section,  it  is  spoken  of  as 
the  magnetic  density,  or  density  of  magnetization,  and  the  unit 
used  is  called  a  Gauss ;  thus  we  speak  of  a  magnet  as  having  a 
density  of  so  many  gausses  per  square  centimeter,  or  square 
inch  of  cross-section.  The  density  of  magnetization  is  deter- 
mined by  a  rule  given  on  page  46. 

The  lifting  capacity  of  a  magnet  can  be  determined  by  the 
following  rule :  — 

TO    FIND    THE    LIFTING    CAPACITY    OF    A    MAGNET    IN    POUNDS. 

Multiply  the  area  of  cross-section  of  the  magnet  pole  in  square 
inches,  by  the  square  of  the  density  of  magnetization  per  square 
inch,  and  divide  this  product  by  72  millions. 

This  rule  gives  the  pull  for  one  pole.  For  horse  shoe  magnets 
double  the  figures.  If  the  object  lifted  is  not  in  contact  with 
the  poles  the  pull  will  be  less  than  rule  gives. 


14  HANDBOOK    ON    ENGINEERING „ 


CHAPTER     II. 
THE  PRINCIPLES  OF  ELECTROMAGNETIC  INDUCTION. 

By  Electromagnetic  Induction,  I  mean  the  induction  of  electric 
currents  by  magnetic  action.  In  the  preceding  chapter  it  has  been 
shown  that  if  we  move  a  wire  through  a  magnetic  field,  an  electric 
current  will  be  generated  in  it,  providing  its  ends  are  joined,  so 
as  to  form  a  closed  circuit.  If  the  ends  are  not  joined,  then  there 
will  be  no  current  developed,  because,  an  electric  current  cannot 
flow  except  in  a  closed  circuit.  When  the  ends  of  the  wire  are 
not  joined,  the  movement  through  the  field  develops  simply  an 
electromotive  force.  Electromotive  force  is  that  force  which 
causes  an  electric  current  to  flow  when  there  is  a  circuit  in  which 
it  can  flow.  Electromotive  force  is  a  long-winded  name  and  on 
that  account  it  is  always  abbreviated  into  e.m.f.,  so  that  here- 
after when  these  letters  are  used,  it  will  be  understood  that  they 
stand  for  electromotive  force. 

Metals  and  all  other  substances  that  allow  electric  currents 
to  flow  through  them  are  called  conductors,  while  glass,  mica, 
wood,  paper  and  many  other  similar  forms  of  matter  that  do  not 
allow  currents  to  flow  through  them  are  called  insulators.  The 
difference  between  conductors  and  insulators  is  only  one  of 
degree,  for  there  is  no  known  substance  that  is  an  absolute  non- 
conductor of  electricity  ;  that  is,  a  perfect  insulator  ;  and  there  is 
no  substance  that  does  not  resist  to  some  extent  the  passage  of  a 
current  —  that  is,  there  is  no  such  thing  as  a  perfect  conductor. 
Some  substances,  like  damp  paper  or  wood,  which  stand  midway 
between  good  conductors  and  good  insulators,  can  be  regarded  as 
either  one  or  the  other,  depending  upon  the  service  for  which  they 
are  used.  For  currents  of  very  low  e.m.f.,  they  would  be  in- 


HANDBOOK    ON    ENGINEERING.  15 

sulators,  but  for  currents  of  very  high  e.m.f.,  they  would  be 
conductors. 

The  current  that  will  flow  through  any  circuit  when  impelled 
by  an  e.m.f.,  will  have  a  strength  that  will  depend  upon  the 
amount  of  resistance  that  opposes  its  flow.  As  all  conducting 
materials  are  not  of  the  same  degree  of  conductivity,  their  relative 
values  are  determined  by  the  amount  of  resistance  they  interpose 
to  the  flow  of  the  current.  The  resistance  of  a  conductor  is 
measured  in  units  called  ohms ;  the  strength  of  current  is 
measured  in  units  called  amperes,  and  the  e.m.f.  is  measured  in 
units  called  volts.  The  relation  between  these  units  is  such  that 
an  e.m.f.  of  one  volt  will  cause  a  current  of  one  ampere  to  flow 
in  a  circuit  having  a  resistance  of  one  ohm. 

When  a  wire  is  moved  through  a  magnetic  field,  the  e.m.f. 
induced  in  it  will  be  determined  by  the  strength  of  the  field  and 
the  velocity  with  which  the  wire  moves,  and  will  not  be  affected 
in  any  way  by  the  resistance  of  the  circuit  of  which  the  wire 
forms  a  part.  If  the  resistance  is  very  great,  the  strength  of 
current  generated  will  be  very  low,,  and  if  the  resistance  is  very 
low  the  current  will  be  strong,  but  in  either  case  the  e.m.f.  will 
be  the  same. 

If  movement  of  the  wire  in  one  direction  develops  an  e.m.f. 
in  a  given  direction  through  the  circuit,  then  movement  of  the 
wire  in  opposite  direction  will  reverse  the  direction  of  the  e.m.f. 
Thus,  in  Fig.  23,  which  represents  a  magnetic  field  between 
the  poles  N  S,  if  wire  a  is  moved  from  right  to  left,  it  will  have 
induced  in  it  an  e.m.f.  that  will  be  from  back  to  front,  and  if 
the  direction  of  motion  of  the  wire  is  reversed,  the  e.m.f.  will 
also  be  reversed.  This  will  be  true  whether  the  wire  is  near  the 
N  pole  or  S  pole.  This  being  the  case,  it  can  be  seen  that  if 
a  represents  the  end  of  a  wire  moving  in  the  direction  of  arrow 
d,  and  6  the  end  of  a  wire  moving  in  the  opposite  direction,  the 
e.m.f. 'sin  these  two  wires  will  be  in  opposite  directions.  The 


16 


HANDBOOK    ON    ENGINEERING. 


direction  of  the  e.m.f.  in  a  will  be  up  from  the  paper  toward 
the  observer,  and  the  direction  of  the  e.m.f .  in  b  will  be  down 
through  the  paper.  If  these  two  wires  are  secured  to  a  shaft 
placed  in  the  center  of  the  field,  then  by  the  continuous  rotation 


Fig.  23. 


Fig.  24, 


of  the  shaft,  the  two  wires  can  be  made  to  revolve  around  the 
circular  path  shown. 

If  these  two  wires  are  joined  at  the  ends,  as  shown  in  Fig.  24, 
they  will  form  a  closed  loop,  and  although  the  direction  of  the 
induced  e.m.f.  in  the  two  sides  will  be  opposite,  when  compared 
to  a  fixed  point  in  space,  they  will  be  in  the  same  direction  so 
far  as  the  loop  is  concerned  ;  that  is,  both  e.m.f.'s  will  develop 
currents  that  will  flow  through  the  wire  in  the  same  directions. 

Returning  to  Fig".  23  it  will  be  noticed  that  if  the  wires  re- 
volve around  the  circular  path  at  a  uniform  velocity,  their  move- 
ment in  the  direction  of  line  c  c  will  not  be  uniform,  but  will  be 
the  greatest  when  the  wires  are  in  the  position  shown,  and  least, 
when  they  cross  the  line  c  c.  In  fact,  when  the  wires  cross  line 
c  c  their  motion  in  the  direction  of  this  line  will  be  zero,  for  this 


HANDBOOK    ON    ENGINEERING. 


17 


is  the  point  where  the  direction  of  movement  reverses.  Now, 
the  magnitude  of  the  e.m.f .  induced  in  the  wire  is  proportional 
to  the  velocity  in  the  direction  of  the  line  c  c,  hence,  when  the 
wires  are  crossing  this  line,  the  e.m.f.  will  be  zero,  and  when 
they  are  one-quarter  of  a  turn  ahead  of  the  line,  the  e.m.f.  will 
be  the  highest. 

In  Fig*  24  we  see  that  in  side  a,  the  direction  of  the  current 
is  toward  the  front,  and  in  b  it  is  the  reverse ;  now,  when  a 
moves  through  half  a  turn,  it  will  take  the  place  of  &,  and  the 
direction  of  the  e.m.f.  induced  in  it  will  be  the  same  as  in  b  in 
the  figure  ;  that  is,  it  will  be  the  reverse  of  what  it  is  when  pass" 
ing  in  front  of  the  pole  N.  This  being  the  case,  it  is  evident 
that  each  time  the  loop  makes  a  half -revolution,  the  direction  of 
the  current  generated  in  it  reverses. 


Fig.  25. 

As  the  loop  in  Fig.  24  is  closed,  the  current  generated  in  it 
would  be  of  no  practical  value,  but  if  we  cut  the  wire  at  one 
side  and  connects  the  ends  with  rings  as  shown  at  a  and  b  in  Fig. 
25,  then  by  means  of  collecting  brushes  c  c  we  can  take  the  cur- 


18 


HANDBOOK    ON    ENGINEERING. 


rent  off  through  the  wires  d  d.  This  current,  however,  would 
consist  of  a  series  of  impulses  that  would  flow  in  opposite  direc- 
tions, each  one  starting  from  nothing  and  increasing  to  its  greatest 


Fig.  26. 

strength  when  the  loop  reaches  the  position  shown  in  the  figure, ' 
and  then  declining  and  reaching  the  zero  value  when  the  loop 
reaches  the  vertical  position.  Such  a  current  is  called  an  alter- 
nating current,  because  it  flows  first  in  one  direction  and  then  in 
the  opposite  direction.  All  forms  of  machines  that  generate  cur- 
rents by  electromagnetic  induction,  develop  alternating  currents, 
but  in  the  class  of  machines  known  as  direct  or  continuous  current, 
a  rectifying  device  is  used  which  rectifies  the  current  before  it 
reaches  the  external  circuit.  This  rectifying  device  is  called  a 
commutator,  and  is  illustrated  in  its  simplest  form  in  Fig  26.  In 
this  illustration  it  will  be  noticed  that  the  ends  of  the  wire,  instead 
of  being  attached  to  two  independent  rings,  placed  side  by  side, 
are  secured  to  two  half-rings,  placed  opposite  each  other.  The 
brushes  c  d,  through  which  the  current  is  taken  off,  are  held 
stationary ;  therefore,  as  can  be  readily  seen,  c  will  make  contact 


HANDBOOK    ON    ENGINEERING. 


19 


with  a  during  one-half  of  the  revolution,  and  with  b  during  the 
other  half  ;  and  this  will  also  be  the  case  with  brush  d.  Now,  as 
the  half-rings  with  which  the  brushes  are  in  contact  change  at 
each  half  revolution,  it  follows  that  by  properly  setting  the 
brushes,  they  can  be  made  to  pass  from  one-half  ring  to  the  other 
at  the  very  instant  when  the  direction  of  the  current  in  the  loop 
reverses,  so  that  through  each  brush  there  will  be  a  succession  of 
current  impulses,  but  all  in  the  same  direction. 

The  device  shown  in  Fig.  25  is  a  perfect  alternating  current 
generator,  and  that  shown  in  Fig.  26  is  a  perfect  direct  current 
generator.  In  both  cases,  however,  the  e.m.f.  induced  is  so 
low  as  to  be  of  no  practical  value.  To  obtain  serviceable 
machines,  capable  of  developing  the  e.m.f.  and  current  strength 
required  in  practice,  it  is  necessary  to  provide  very  strong  mag- 
netic fields  and  to  rotate  in  these  a  large  number  of  loops  of  wire. 
In  order  that  the  operation  of  such  machines  may  be  understood, 
I  will  first  show  how  the  powerful  magnetic  fields  are  obtained. 

In  Fig".  27  two  wires  are  shown  as  seen  from  the  end,  these 
being  marked  A  and  B.  The  lines  of  force  surrounding  them  are 


'^ifj 

's  / 


Fig.  28. 


Fig.  27. 


in  directions  that  correspond  to  opposite  directions  of  current  in 
the  wires.  In  wire  A,  the  current  flows  away  from  the  observer. 
As  can  be  seen,  the  lines  of  force  of  both  wires  have  to  crowd  into 


20  HANDBOOK    ON    ENGINEERING. 

the  space  between  the  wires,  for  on  the  outside  of  A  the  two  sets 
of  lines  would  meet  each  other  head  on,  and  this  would  also  be 
the  case  on  the  right  side  of  wire  B.  This  crowding  of  the  lines 
of  force  into  the  space  between  the  wires  causes  them  to  distort 
from  their  natural  position  and  instead  of  being  central  with  the 
wires,  are  eccentric  to  them.  If  we  take  a  long  wire  through 
which  a  current  is  flowing  and  bend  it  into  a  loop,  we  will  see 
that  if  the  current  flows  out  through  one  side,  it  will  return 
through  the  other  side,  so  that  in  the  two  sides  of  the  loop  the 
current  will  flow  in  opposite  directions.  This  being  the  case, 
Fig.  27  can  be  regarded  as  showing  the  two  sides  of  such  a  loop, 
and  from  it  we  find  that  the  effect  of  such  a  loop  is  to  concentrate 
within  its  interior  nearly  all  the  lines  of  force  that  surround  the 
wire. 

In  Fig*  28  the  two  wires  A  and  B  are  surrounded  with  lines 
of  force  that  correspond  to  the  same  direction  of  current.  In 
this  case  it  will  be  noticed  that  in  the  space  between  the  wires  the 
lines  of  force  flow  in  opposite  directions  ;  hence,  only  a  few  of  the 
lines  will  follow  this  path,  simply  that  number  surrounding  each 
wire  that  can  traverse  the  space  without  encroaching  upon  the 
path  of  the  lines  belonging  to  the  other  wire.  If  the  two  wires 
are  very  near  to  each  other,  practically  all  the  lines  of  force  of 
both  wires  will  join  forces,  so  to  speak,  and  pass  around  the  two 
wires.  Now,  if  we  wind  a  wire  into  a  coil  of  many  turns,  the 
direction  of  the  current  in  the  several  turns  will  be  the  same,  so 
that  the  lines  of  force  of  all  the  turns  will  combine  into  one  large 
stream  and  circulate  around  the  entire  coil  side,  no  matter  how 
many  turns  of  wire  it  may  contain.  From  this  it  can  be  seen 
that  if  we  have  a  current  of  say  ten  amperes,  we  can  make  it 
produce  just  as  powerful  magnetic  effect  as  a  current  of  one 
thousand  amperes,  by  simply  increasing  the  number  of  turns  of 
wire  in  the  coil.  A  current  of  ten  amperes  passing  through  a  coil 
of  wire  containing  one  hundred  turns,  will  have  the  same  magnet- 


HANDBOOK    ON    ENGINEERING. 


21 


ism  in  effect,  as  a  current  of  one  hundred  amperes  passing  through 
a  coil  of  ten  turns,  or  as  a  current  of  one  thousand  amperes  pass- 
ing through  a  coil  of  a  single  turn. 

If  we  place  at  the  side  of  a  wire  through  which  an  electric 
current  is  flowing  a  piece  of  iron,  as  is  shown  in  Fig.  29,  the 
effect  will  be  that  the  lines  of  force  will  no  longer  flow  in  circular 
paths,  as  indicated  by  the  circle  a,  but  will  be  deflected  in  the 
manner  illustrated,  by  the  presence  of  the  iron.  If,  instead  of 


Fig.  29. 


Fig.  30. 


the  straight  iron  bar,  we  substitute  a  ring  of  iron,  as  in  Fig.  30, 
nearly  all  the  lines  of  force  will  be  concentrated  in  the  metal,  and 
the  magnetic  field  in  the  space  (7,  between  the  ends  of  the  ring, 
will  be  vastly  greater  than  at  any  other  point.  The  explanation 
of  these  actions  is  that  all  forms  of  matter  oppose  the  develop- 
ment of  magnetic  force,  but  some  offer  greater  resistance  than 
others.  Iron,  steel,  nickel,  and  one  or  two  other  metals,  offer 
less  resistance  to  the  magnetic  lines  of  force  than  air,  and  are 
said  to  have  a  higher  magnetic  permeability.  Nickel  is  only  a 
slight  improvement  on  air,  but  steel  and  iron  are  far  superior, 
iron  being  of  about  two  to  three  times  the  permeability  of  hard- 


22 


HANDBOOK    ON    ENGINEERING. 


ened  steel,  and  about  one  thousand  times  the  permeability  of  air, 
when  magnetized  to  the  density  ordinarily  used  in  practice.  The 
iron  in  Figs.  29  and  30,  therefore,  becomes  the  path  of  the  lines 
of  force,  because  it  interposes  a  much  lower  resistance.  Owing 
to  this  difference  in  the  resistance  of  iron  and  air,  it  is  possible 
to  make  an  iron  magnet  core  of  any  desired  form,  and  to  con- 
centrate within  it  nearly  all  the  lines  of  force  developed  by  the 
current  flowing  through  the  wire  wound  upon  it.  The  presence 
of  the  iron  not  only  serves  to  concentrate  the  magnetism  in  it, 
but  as  it  reduces  the  resistance  opposing  the  development  of 
the  magnetism,  it  enables  the  field  to  be  made  vastly  stronger 
than  it  could  be  with  air  alone,  say  a  thousand  times  as  great. 

If  we  make  a  magnet  in  the  form  of  Fig.  31,  with  a  coil  of 
wire  around  the  part  5,  practically  all  the  lines  of  force  will  flow  to 


Fig.  31. 

the  poles  N  /S,  and  will  pass  through  the  air  space  between  them. 
If  this  air  space  is  nearly  filled  with  a  cylindrical  mass  of  iron,  J., 
the  strength  of  the  magnet  will  be  increased,  for,  by  doing  this, 


HANDBOOK    ON    ENGINEERING. 


23 


we  replace  air  which  is  a  poor  magnetic  conductor,  by  iron  which 
is  a  far  superior  conductor.  Electric  motors  and  generators  are 
made  with  a  cylindrical  mass  of  iron  at  A,  which  is  the  armature 


Fig.  32. 


Fig.  33. 


core,  and  the  air  space  between  it  and  the  faces  of  the  poles  of  the 
field  magnet  is  made  just  sufficient  to  accommodate  the  wire 
coils,  and  by  this  means  the  field  strength  is  increased  as  much  as 
possible. 

The  armature  cores  are  sometimes  made  solid,  as  in  Fig.  32, 
and  sometimes  as  a  ring,  as  in  Fig.  33.  When  they  are  solid, 
the  lines  of  force  cross  through  them  in  straight  lines,  see  Fig. 
32  ;  and  when  they  are  ring  form,  the  lines  follow  the  ring  and  do 
not  penetrate  the  interior  space. 

If  the  single  loop  of  Fig.  24  is  replaced  by  a  coil  containing 
many  turns  of  wire,  the  e.m.f.  induced  in  it  will  be  increased  in 
proportion  with  the  number  of  turns  of  wire  in  the  coil,  so  that  by 
using  such  a  coil  in  a  field  such  as  shown  in  Fig.  31,  a  high 
e.m.f.  can  be  obtained.  This  e.m.f.,  however,  would  be  alter- 
nating, and  if  the  current  were  rectified  by  means  of  a  commu- 


24 


HANDBOOK    ON    ENGINEERING. 


tator,  it  would  not  be  of  uniform  strength,  but  would  fluctuate 
from  a  maximum  value  to  zero.  Just  how  the  current  would 
fluctuate  and  how  the  construction  can  be  changed  so  as  to  get  rid 
of  the  fluctuation,  we  can  explain  by  presenting  a  diagram  that 
illustrates  the  alternating  current  as  it  flows  in  the  armature  coil, 
and  the  rectified  current  as  it  leaves  the  commutator. 

In  Fig.  34,  let  the  distance  /  7i,  h  i,  i  n,  along  the  line// 
represent  half -revolutions  of  the  coil,  and  let  distances  measured 
on  the  vertical  line  c  d  represent  the  strength  of  current,  distances 
above/  being  current  flowing  in  one  direction,  and  distances  below 
/being  for  current  flowing  in  the  opposite  direction.  Let  us  con- 
sider the  instant  when  the  coil  is  passing  the  point  where  the 
e.m.f .  induced  is  zero ;  then  this  instant  will  be  represented 
by  the  point  /,  at  the  left  of  the  diagram,  and  the  curve  a 
will  start  from  this  point ;  as  at  that  instant,  the  current  which  it 
represents  has  no  value.  As  the  coil  rotates,  the  current  begins 
to  grow,  and  this  fact  we  indicate  by  causing  curve  a  to  gradually 


Fig.  34.  f 


d 


Fig.  35. 


rise  above  the  horizontal  line.  At  the  quarter  turn,  the  current 
reaches  its  greatest  strength,  thus  this  forms  the  highest  point  of 
curve  a,  and  is  midway  between  /  and  h.  From  this  point 


HANDBOOK    ON    ENGINEERING. 


25 


onward,  the  current  declines  and  becomes  zero,  when  the  rotation 
of  the  coil  has  reached  one-half  of  a  revolution,  which  is  repre- 
sented by  the  point  h.  In  the  next  half -re  volution,  the  current 


Fig.  36. 


Fig.  38. 


flows  in  the  reverse  direction,  but  has  the  same  maximum  strength 
and  increases  and  decreases  at  the  same  rate  ;  therefore,  the  curve 
6,  drawn  below  the  horizontal  line,  represents  the  reverse  current ; 
and  point  i  corresponds  to  one  complete  revolution,  so  that 
beyond  i  the  curves  a  and  b  are  repeated  in  systematic  order. 

Now,  if  we  provide  a  commutator  to  rectify  this  current,  all 
we  can  accomplish  is  to  turn  curve  b  upside  down  and  transfer  it 
to  the  upper  side  of  the  horizontal  line,  as  in  Fig.  35  ;  but,  as 
will  be  seen,  all  we  accomplish  by  this  act  is  to  obtain  a  current 
that  flows  always  in  the  same  direction,  but  at  each  half -revo- 
lution it  drops  down  to  a  zero  value. 

If  we  wind  two  coils  upon  the  armature,  placing  them  at  right 
angles  with  each  other,  as  is  indicated  by  A  and  B  in  Fig.  36, 
then  if  the  currents  of  these  two  coils  are  rectified,  they  will  bear 
the  relation  toward  each  other  shown  at  the  upper  line  in  Fig.  37, 
the  a  a  curves  in  solid  lines  representing  the  current  from  the  A 
coil,  and  the  b  b  curves  in  broken  lines,  representing  the  current 
from  the  B  coil.  As  will  be  seen,  when  one  of  these  currents  is 
zero,  the  other  is  at  its  greatest  value,  so  that  if  we  run  both  into 


26  HANDBOOK    ON    ENGINEERING. 

the  same  circuit,  the  lowest  value  of  the  combined  current  would 
be  equal  to  the  maximum  of  either  one  of  the  single  currents, 
and  the  maximum  value  would  be  equal  to  the  sum  of  the  two 
currents  when  the  coils  are  on  the  eighths  of  the  revolution. 


Fig.  37. 

This  resulting  current  is  shown  on  the  lower  line  in  Fig.  37  by 
the  curve  d  d.  From  this  curve  we  see  that  the  number  of 
fluctuations  in  the  current  has  been  doubled,  but  the  variation  in 
the  strength  is  greatly  reduced.  If  we  wound  four  coils  upon 
the  armature,  as  indicated  by  A  B  C  D,  in  Fig.  38,  the  number 
of  undulations  in  the  combined  current  would  be  again  doubled, 
but  the  fluctuation  would  be  very  much  less.  If  the  number  of 
coils  is  increased  to  twenty-five  or  thirty,  the  fluctuations  in  the 
current  become  so  small  a.s  to  be  hardly  worth  noticing. 

With  coils  such  as  shown  in  Fig.  26,  a  separate  commutator 
would  have  to  be  provided  for  each  coil,  and  this  would  render 
the  machine  very  complicated,  if  the  number  of  coils  were  even 
six  or  eight ;  hence,  in  actual  machines,  the  winding  of  the  coils 
is  modified  so  as  to  be  able  to  use  a  single  commutator  for  any 
number  of  coils.  This  construction  will  be  explained  in  the 
next  chapter. 


HANDBOOK    ON    ENGINEERING. 


27 


CHAPTER     III. 
TWO  POLE  GENERATORS  AND  MOTORS. 

The  simplest  type  of  armature  winding  is  that  used  with  ring 
cores,  and  is  illustrated  in  Fig.  39.  As  will  be  seen,  it  is  simply 
a  continuous  winding  all  the  way  around  the  circle,  the  end  of 
the  last  turn  of  wire  being  connected  with  the  beginning  of  the 
first  turn,  so  as  to  form  an  endless  coil.  If  wires  are  attached  at 
a  and  6,  and  a  current  is  passed  through,  it  will  divide  into  two 
halves,  one  part  flowing  through  the  wire  above  a  6,  and  the  other 
part  through  the  wire  below  a  b.  In  the  upper  half  of  the  wire, 
the  direction  of  the  current  in  the  front  sides  of  the  turns  will  be 
toward  the  center  of  the  ring,  as  is  indicated  by  the  arrow  heads, 
and  in  the  lower  half  it  will  be  away  from  the  center.  If,  in- 


stead of  attaching  wires  at  a  and  l>  we  place  stationary  springs,  so 
as  to  press  against  the  wire,  then  we  could  revolve  the  ring,  and 
still  the  current  would  enter  and  leave  the  wire  at  the  same  points. 
Small  armatures  are  often  made  in  this  way,  but  for  regular 


28  HANDBOOK    ON    ENGINEERING. 

machines  it  is  more  desirable  to  provide  a  commutator  as  shown 
in  Fig.  40  at  C,  and  then  the  several  segments  can  be  connected 
with  the  wire  at  regular  intervals.  In  the  figure,  the  commutator 
is  provided  with  twelve  segments,  and  these  connect  with  the 
armature  wire  at  every  fourth  turn,  so  that  the  wire  is  divided 
into  twelve  coils  of  four  turns  each. 

The  only  difference  between  this  diagram  and  a  regular  gen- 
erator armature  of  the  ring  type,  is  that  it  shows  the  wire  coils 
spread  out  with  a  considerable  space  between  them,  and  only  in 
one  layer,  while  in  the  actual  machine,  the  wire  is  wound  close 
together  and  generally,  in  several  layers  ;  but  no  matter  how  many 
layers  there  may  be,  or  how  many  turns  in  a  coil,  the  principle  of 
winding  is  the  same. 

I  have  shown  the  ring  winding  first,  because  it  is  so  simple 
that  it  can  be  understood  with  the  most  superficial  explanation. 
The  drum  winding,  which  is  used  to  a  much  greater  extent,  is  the 
same  in  principle  as  the  ring,  but  owing  to  the  fact  that  the  coils 
cross  each  other  at  the  ends,  it  appears  to  be  decidedly  different. 
By  the  aid  of  Figs.  41  to  44,  the  drum  winding  can  be  made  per- 
fectly clear. 

Fig*  41  shows  a  ring  armature  core  with  a  single  coil  wound 
upon  it ;  and  Fig.  42  shows  a  drum  core,  with  a  single  coil  wound 
upon  it.  In  the  ring,  only  one  side  of  the  coil  appears  upon  the 
outer  surface  of  the  armature,  but  in  the  drum,  as  there  is  no 
open  space  for  the  coil  to  thread  through,  both  sides  of  the  coil 
must  be  placed  upon  the  outer  surface.  The  side  B  of  the  coil 
may  be  called  the  live  side,  as  it  is  the  one  from  which  the  ends 
project,  and  the  lower  side  c,  may  be  called  the  dead  side.  Since 
only  the  live  side  of  the  coil  has  ends  to  be  connected,  it  can  be 
readily  seen  that  if  in  the  drum  winding  we  leave  spaces  between 
the  live  sides  for  the  dead  sides,  and  then  connect  the  ends  of  the 
live  sides  by  jumping  over  the  dead  side  between  them,  that  we 
will  have  the  same  order  of  connection  as  in  the  ring  winding. 


HANDBOOK    ON    ENGINEERING. 


29 


Fig.  41. 

The  dead  side  of  each  coil  adjoins  the  live  side  of  a  coil  that  is,  in 
reality,  half  a  circumference  away  from  it;  thus,  in  Fig.  43,  the 
live  side  of  coil  a  is  at  the  top  and  the  dead  side  is  at  the  bottom  ; 
while  the  live  side  of  coil  n  is  at  the  bottom  and  the  dead  side  is 
at  the  top.  The  live  sides  of  these  two  coils  are  on  opposite  sides 
of  the  armature,  so  that  the  coil  side  to  the  right  of  a  is  simply 


Fig.  43, 


Fig.  44, 


30  HANDBOOK    ON    ENGINEERING. 

the  dead  side  of  a  coil  whose  live  side  is  on  the  other  side  of  the 
diameter.  In  Fig.  44  the  two  coils  a  and  b  are  adjoining  coils, 
for  the  coil  side  between  them  is  the  dead  side  of  coil  n.  To  con- 
nect the  armature,  therefore,  we  join  end  2  of  coil  a  with  end  1 
of  coil  Z>,  and  the  end  2  of  coil  b  would  jump  over  a  dead  side  and 
connect  with  end  1  of  coil  c.  Coil  c,  however,  would  appear  to 
be  two  coils  ahead  of  &,  just  as  6  appears  to  be  two  coils  ahead 
of  a. 

In  winding  drum  armatures,  the  coils  are  generally  placed  in 
pairs,  as  shown  in  Fig.  43  and  also  in  Fig.  44.  The  object  of 
this  is  simply  to  make  the  ends  of  the  armature  look  more  even- 
A  drum  armature  can  be  wound  out  of  a  continuous  wire,  by 
simply  making  a  loop  to  take  the  place  of  the  ends  1  and  2 ,  and 
then  skipping  a  space,  as  shown  by  coils  a  and  b  in  Fig.  44.  After 
the  armature  is  half  covered,  there  will  be  spaces  left  between  the 
coils,  these  spaces  being  of  the  width  of  a  coil ;  we  then  proceed 
to  fill  up  the  vacant  spaces,  and  when  they  are  all  filled,  the  last 
coil  put  in  will  be  the  proper  position  to  connect  with  the  first 
one  wound.  A  little  practice  with  a  piece  of  twine  and  a  wooden 
cylinder,  will  enable  any  one  to  find  out  in  short  order  how  to 
wind  drum  armatures. 

The  two  types  of  winding  I  have  explained,  are  those  used 
with  two  pole  machines,  motors  as  well  as  generators.  I  may 
here  add  that  there  is  no  difference,  electrically,  between  a  motor 
and  a  generator,  and  any  machine  can  be  used  for  either  service. 
Motors,  however,  are  somewhat  modified  in  design  so  as  to  make 
them  more  suited  to  the  work  they  have  to  perform.  The  modi- 
fication consists  mainly  in  protecting  the  parts  liable  to  be  injured 
by  objects  falling  upon  them. 

The  general  arrangement  of  the  field  and  armature  in  a  two 
pole  machine  is  shown  in  Fig.  31.  The  design  can  be  changed  in 
a  vast  number  of  ways,  but  it  will  always  be  two-pole,  or  bipolar, 
as  it  is  called,  if  only  two  poles  are  presented  to  the  armature. 


HANDBOOK    ON    ENGINEERING. 


31 


Generators  and  motors  are  arranged  so  that  the  current  that 
magnetizes  the  field  may  be  the  whole  current  that  flows  in  the 
circuit,  or  only  a  part  of  it.  When  the  whole  current  passes 
through  the  field  magnetizing  coils,  the  machine  is  said  to  be  of 
the  series  type ;  this  name  being  given  because  the  armature  wire 
and  the  field  coils  are  connected  in  series,  so  that  the  current  first 
passes  through  one  and  then  through  the  other.  If  the  field 
coils  are  traversed  by  only  a  portion  of  the  current,  the  machine 


Fig.  45. 


Fig.  46. 


is  said  to  be  of  the  shunt  type,  owing  to  the  fact  that  the  field  is 
supplied  with  a  current  that  is  shunted  from  the  main  circuit. 
Generators  and  motors  are  also  arranged  so  that  there  are  two 
sets  of  field  coils  and  one  is  traversed  by  the  whole  current,  and 
the  other  by  a  portion  thereof.  The  best  way  to  understand 
these  different  types  of  connection  is  by  means  of  simple  diagrams 
that  show  the  wire  coils  of  the  field  and  the  outline  of  the  arma- 
ture. Such  diagrams  are  presented  in  Figs.  45  to  50.  Fig.  45 


32 


HANDBOOK    ON    ENGINEERING. 


represents  the  series  connection,  A  being  the  armature,  C  the 
commutator,  and  M  the  field  coil.  The  direction  of  the  current 
is  indicated  by  the  arrow  heads.  Fig.  46  is  the  shunt  connection, 
and  the  arrow  heads  show  the  direction  of  the  currents  in  the  case 
of  a  generator.  As  will  be  seen,  at  d  the  field  current  branches 
off  from  the  main  line  and  returns  to  it  at  a,  after  having  passed 
through  the  field  coil.  Fig.  47  shows  the  type  in  which  the  field  is 
magnetized  by  two  sets  of  coils,  one  being  in  series  with  the  main 
circuit  and  the  other  in  shunt.  As  will  be  noticed,  all  the 
armature  current  passing  out  through  wire  cZ,  goes  through  coil 
jp7,  except  the  portion  that  is  shunted  at  c,  into  the  shunt  coil  M. 
This  type  of  winding  is  called  compound,  being  a  combination 
of  the  series  and  shunt.  When  the  shunt  coil  is  connected  as  in 


Fig.  47. 


Fig.  48. 


Fig.  47,  it  is  called  a  short  shunt,  and  when  as  in  Fig.  48,  it  is  a 
long  shunt.  In  the  first  case,  the  coil  M  shunts  the  armature 
only,  and  in  the  second,  it  shunts  the  coil  F  also. 


HANDBOOK    OX    EMJINKKHINU. 


33 


Figs*  49  and  50  show  the  shunt  and  compound  types  for 
motors,  and  as  will  be  noticed,  the  only  difference  between  them 
and  the  generator  diagrams,  is  that  the  direction  of  the  current 


d 


Fig.  49. 


Fig.  50. 


in  the  shunt  coils  is  not  the  same.  This  difference  in  direction  is 
due  to  the  fact  that  in  the  generator  the  armature  generates  the 
current  that  passes  through  coil  M;  hence,  at  point  d!,  the  cur- 
rent flows  up  to  the  main  line  and  down  to  the  field  coil.  In  the 
motor,  the  current  comes  from  an  external  source  through  main 
ft,  and  thus  passes  from  a  to  the  armature,  and  also  to  the  field 
coil,  thus  traversing  the  latter  in  the  opposite  direction.  In  the 
series  coil  F,  the  direction  of  the  current  is  the  same  in  both 
machines. 

Generators  are  made  so  as  to  keep  the  strength  of  the  current 
constant,  and  allow  the  voltage  to  vary  as  the  demands  of  the 
service  may  require ;  or  they  may  be  wound  so  as  to  keep  the 
voltage  constant  and  allow  the  current  strength  to  vary.  Machines 

3 


34  HANDBOOK    ON    ENGINEERING. 

of  the  first  class  are  called  constant  current,  and  are 
used  principally  for  arc  lighting.  Machines  of  the  second 
class  are  called  constant  potential  and  are  the  kind  used 
for  incandescent  lighting,  for  electric  railways  and  for  the 
operation  of  motors  of  every  description.  For  constant  current 
generators  the  series  winding  is  used  in  connection  with  some 
kind  of  regulating  device  that  prevents  the  current  strength  from 
varying  more  than  the  small  fraction  of  an  ampere.  The  shunt 
and  compound  windings  are  used  for  constant  potential  genera- 
tors. If  the  armature  wire  had  no  resistance,  the  shunt  winding 
would  enable  a  generator  to  maintain  a  constant  voltage  at  its 
terminals,  no  matter  how  much  the  strength  of  the  current  might 
vary ;  but  armature  without  resistance  cannot  be  made ;  there- 
fore, a  shunt- wound  machine  will  develop  a  slightly  lower  voltage 
with  full  current  than  with  a  weak  one,  but  the  difference  will 
not  be  more  than  three  to  five  per  cent.  By  the  aid  of  the  com- 
pound winding,  the  generator  can  be  made  so  as  to  develop  the 
same  voltage  with  light  or  full  load,  and  if  desired,  the  voltage 
can  be  made  to  increase  as  the  current  increases.  If  a  com- 
pound generator  is  so  proportioned  that  the  voltage  is  the  same 
for  weak  and  strong  currents,  it  is  said  to  be  evenly-compounded, 
and  if  the  voltage  increases  as  the  current  increases,  it  is  said  to 
be  over-compounded.  If  the  voltage  is  five  per  cent  higher,  with 
full  load  than  with  no  load,  the  generator  is  said  to  be  over-com- 
pounded five  per  cent,  and  if  the  increase  is  ten  per  cent,  it  is 
said  to  be  over-compounded  ten  per  cent. 

The  way  in  which  a  compound  generator  increases  the  volt- 
age can  be  readily  understood  from  an  examination  of  Fig.  47. 
The  current  that  passes  through  the  shunt  coil  Jf,  is  practically 
one  of  the  same  strength  at  all  times ;  therefore,  the  magnet- 
izing effect  of  this  coil  does  not  change.  Through  coil  F  the 
whole  current  passes,  hence,  the  magnetizing  effect  of  this  coil 
increases  as  the  current  strength  increases.  Now  the  total  field 


HANDBOOK    ON    ENGINEERING.  35 

magnetism  is  that  due  to  the  combined  action  of  the  two  coils,  so 
that  as  the  action  of  F  increases,  the  strength  of  the  field  in- 
creases. If  F  has  only  a  few  turns  of  wire,  it  will  only  help 
slightly  to  magnetize  the  field ;  therefore,  its  increased  effect,  due 
to  increase  in  current,  will  not  be  very  noticeable ;  but  if  F  has 
many  turns,  it  will  develop  a  large  proportion  of  the  field  magnet- 
ism, and,  under  this  condition,  the  change  in  current  strength 
will  make  a  decided  change  in  the  strength  of  the  field,  and  thus 
in  the  voltage,  for  the  voltage  is  directly  proportional  to  the 
strength  of  the  field. 

In  motors,  the  coil  F  can  be  connected  so  as  to  act  with 
coil  MI  or  against  it.  If  both  coils  act  together,  the  motor  is 
compound-wound  ;  and  if  F  acts  against  M ,  the  motor  is  differ- 
entially-wound. A  compound- wound  motor  will  slow  down  more 
with  a  heavy  load  than  a  simple  shunt  machine,  but  it  will  carry 
the  load  with  a  smaller  current,  and,  on  this  account,  this  wind- 
ing is  commonly  used  for  elevator  motors.  A  differential  motor 
will  hold  up  the  speed  better  with  a  heavy  load  than  a  simple 
shunt  machine,  but  it  will  take  a  correspondingly  larger  current 
to  do  the  work.  The  differential  winding  is  not  used  to  any  great 
extent,  except  in  cases  where  it  is  desired  to  obtain  as  uniform  a 
velocity  as  possible. 

In  explaining1  the  principles  of  armature  winding,  it  was  shown 
that  the  commutator  brushes  must  make  contact  with  the  com- 
mutator on  the  sides,  that  is,  that  in  Fig.  51,  they  would  be 
placed  on  the  diameter  n  n.  In  actual  machines,  they  are  either 
ahead  of  this  line,  as  in  Fig.  52,  or  back  of  it,  as  in  Fig.  53. 
The  first  position  is  that  of  the  generator  and  the  second  that  of 
the  motor.  The  reason  why  the  brushes  have  to  be  set  ahead  of 
line  n  n  in  a  generator,  and  back  of  the  line  in  a  motor,  is  that 
the  armature  current  develops  a  magnetization  of  its  own,  and  this 
reacts  upon  the  magnetism  of  the  field  so  as  to  twist  the  lines  of 
force  out  of  their  true  path.  If  we  look  at  Fig.  39,  we  can  see 


36 


HANDBOOK    ON    ENGINEERING . 


that  the  direction  of  the  current  through  the  wires  is  such  that 
the  magnetizing  effect  produced  upon  the  armature  core  is  the 
same  as  it  would  be  if  the  wire  were  wound  in  the  way  indicated 
by  the  vertical  lines  in  Fig.  51.  Now  this  current  will  develop  a 
magnetization  in  the  direction  of  line  n  n;  that  is,  at  right  angles 
to  the  field  magnetism.  These  two  magnetic  forces  of  the  arma- 
ture and  the  field,  engage  in  a  tug  of  war,  and  the  result  is  that 
the  actual  magnetization  that  acts  upon  the  armature  wire  is  the 
combined  effect  of  the  two.  If  the  strength  of  the  field  magnetism 


Fig.  51 


Fig.  52. 


is  proportional  to  line  c  «.,  and  the  strength  of  the  armature  mag- 
netization is  proportional  to  line  <•  b,  then  the  actual  magnetiza- 
tion will  be  equal  to  line  c  d,  and  in  the  direction  d  d  In  Fig. 
52,  which  represents  a  generator,  if  the  current  in  the  field  coils 
passes  over  the  front  side  in  the  direction  of  arrow  ?',  and  the 
armature  revolves  in  the  direction  of  arrow  d,  then  the  armature 
current  will  be  in  the  direction  of  arrow  /  and  the  armature  mag- 
netization will  be  in  the  direction  of  arrow  h.  The  field  magneti- 
zation will  be  from  j^to  S,  therefore,  the  resulting  magnetization 
will  be  in  the  direction  of  line  a  a.  Now  the  proper  position  for 


HANDBOOK    ON    ENGINEERING. 


37 


the  brushes  is  on  a  line  at  right  angles  to  the  direction  of  the 
field,  hence,  they  must  rest  upon  line  c  c.  If  the  machine  is  a 
motor,  the  only  change  effected  will  be  that  the  direction  of  the 
armature  current  will  be  reversed,  so  that  arrow./  will  point 
downward  instead  of  upward,  and  the  magnetism  of  the  armature 
will  be  directed  to  the  right  as  shown  by  arrow  c.  Under  these 
conditions,  the  actual  direction  of  the  field  magnetism  will  be  that 
of  line  b  />,  and  upon  line  e  e,  at  right  angles  to  this  the  brushes 
must  be  set. 


38 


HANDBOOK    ON    ENGINEERING. 


CHAPTER     IV. 
MULTIPOLAR  MACHINES. 

The  only  difference  between  a  bipolar  and  multipolar  machine 
is,  that  the  latter  has  two  poles,  and  the  former  has  two  or  more 
pairs  of  poles.  In  consequence  of  this  difference  in  the  number 


Fig.  54. 

of   poles,  the  armature  winding  has  to  be  slightly  modified,  as  will 
be  presently  explained.     Fig.  54  illustrates  a  four-pole  machine 


HANDBOOK    ON    ENGINEERING. 


39 


and,  as  will  be  noticed,  the  N  and  8  poles  alternate  around  the 
circle.  This  arrangement  is  followed,  no  matter  what  the  number 
of  poles  may  be. 

The  advantage  of  the  multipolar  construction  is  that  it  in. 
creases  the  capacity  of  the  machine  for  a  given  size  and  weight- 
Figs.  55  to  57  illustrate  the  gain  effected  in  weight.  The  first 
figure  shows  a  two-polfe  machine,  the  second  a  four-pole  and  the 
third  an  eight-pole,  the  three  being  of  the  same  capacity.  The 
poles  of  the  second  machine  are  half  as  wide  as  those  of  the  first, 
as  there  are  twice  as  many.  The  other  parts  are  reduced  in  like 
proportion.  In  Fig.  57,  the  poles  are  one-quarter  as  wide  as  in 


Fig.  55. 


Fig.  56. 


Fig.  57. 


Fig.  55,  as  there  are  four  times  as  many.  On  account  of  the 
reduction  in  the  width  of  the  poles,  the  armatures  can  be  increased 
in  diameter  as  the  number  of  poles  is  increased,  without  increas- 
ing the  outside  dimensions  of  the  machine,  so  that  in  reality, 
Fig.  56  is  somewhat  more  powerful  than  Fig.  55,  and  Fig.  57  is 
still  more  powerful. 

The  fields  of  multipolar  machines  are  wound  the  same  as 
those  of  the  bipolar ;  that  is,  as  series,  shunt  or  compound. 
Figs.  58  to  60  show  the  three  types  of  winding  for  a  four-pole 
machine  and  Fig.  61  is  a  diagram  of  compound  winding  for  an 
eight-pole  generator.  The  number  of  commutator  brushes  used  is 
equal  to  the  number  of  poles,  although  with  one  type  of  armature 


40 


HANDBOOK    ON    ENGINEERING. 


winding,  two  brushes  are  suilicient,  no  matter  how  many  poles 
the  machines  may  have.  In  practice,  however,  even  with  this 
winding,  the  number  of  brushes  is  generally  made  equal  to  the 
number  of  poles. 

With  a  four-pole  machine  the  brushes  can  be  connected  in  a 
simple  manner,  as  shown  in  Figs.  58  to  60,  but  with  a  greater 
number  of  poles,  two  rings  are  generally  provided,  to  which  the 
brushes  are  connected  in  the  manner  shown  in  Fig.  61. 


Looking;  at  Fig*  54,  it  can  be  seen  that  if  the  current  flows  up 
from  the  paper,  under  the  N  poles,  it  will  flow  down  through  the 
paper,  under  the  S  poles ;  hence,  the  armature  coils  in  a  four- 
pole  machine  must  span  only  one-quarter  of  the  circumference, 
and  not  one-half,  as  in  the  two-pole  armature.  For  a  six-pole 
armature,  the  coils  must  span  one-sixth  of  the  circumference, 
and  for  an  eight-pole,  one-eighth,  and  so  on,  for  any  higher 
number  of  poles. 

There  are  two  types  of  winding  for  multipolar  armatures,  one 
being  called  the  lap,  or  parallel  winding,  and  the  other  the  wave 


HANDBOOK    ON    ENGINEERING. 


41 


42 


HANDBOOK    ON    ENGINEERING. 


or  series  winding.     Fig.  62  is  a  diagrammatic  illustration  of  the 
lap  winding,  and  Fig.  63  of  the  wave  winding,  both  for  four  poles. 


Fig.  62. 

The  small  circles  around  the  outside  of  the  armature  represent 
bars  or  wires,  which  are  connected  with  the  commutator  segments 
by  means  of  the  solid  lines,  and  with  each  other  at  the  opposite 
side  of  the  armature,  by  means  of  the  broken  lines. 

If  we  start  from  coil  side,  or  bar  1  on  the  left,  and  follow  the 
connections  as  guided  by  the  numbers,  we  will  finally  reach  32, 
and  thus  come  back  to  left  side  brush  a,  which  is  the  starting 
point,  As  will  be  seen,  bar  1  connects  at  the  back  of  armature, 


HANDBOOK    ON    ENGINEERING. 


43 


with  bar  2,  and  then  over  the  front,  the  connection  runs  in  the 
backward  direction,  to  bar  3  ;  thence,  forward  again,  at  the  back 
end,  to  bar  4,  and  again  backward  over  the  front,  to  bar  5.  The 
connections,  therefore,  lap  over  each  other  and  it  is  on  this 
account,  that  it  is  called  a  lap  winding. 

Figf*  63  shows  the  wave  winding,  and  it  will  be  noticed  that  if 
we  start  from  bar  1  at  the  top,  we  advance  around  the  right  to  bar 
2,  and  then  we  go  further  ahead  to  bar  3,  and  in  like  manner 
advance  to  bar  4,  the  connections  in  every  case  advancing  in  the 


Fig.  63. 

same  direction  around  the  circle.     It  will  be  further  noticed  that 
the  connections  run  zig-zag  from  side  to  side  of  the  armature  core 


44  HANDBOOK    ON 

as  they  advance,  thus  forming  a  wave-like  path  for  the  current-. 
and  it  is  on  this  account  that  this  stle  of  connection  is  cjilled 
wave  winding. 

With  the  lap  winding,  the  brushes  a  a  are  connected  with  each 
other,  and  so  are  the  b  I  brushes.  In  the  wave  winding,  two 
brushes  set  one-quarter  of  the  circle  from  each  other,  will  take 
the  current  off  properly  as  indicated  by  a  and  b  in  Fig.  63,  but 
four  brushes  can  also  be  used. 

In  Figf*  54,  the  brushes  are  shown  midway  between  the  poles, 
while  in  Figs.  62  and  63,  they  are  opposite 'the  poles.  This  dif- 
ference 'in  position  is  due  to  the  fact  that  in  the  last  two  named 
figures,  the  connections  between  the  armature  coils  and  the  com- 
mutator segments  do  not  run  in  radial  lines  from  either  side,  but 
one  connection  bends  backward  and  the  other  forward.  In 
actual  machines,  the  connections  are  run  as  in  these  diagrams,  and 
in  some  cases,  one  of  the  sides  runs  in  a  radial  direction ;  there- 
fore, in  some  generators,  the  brushes  are  opposite  the  poles,  and 
in  others  they  are  between  them. 

Diagrams  62  and  63  show  coils  of  a  single  turn,  but  by  regard- 
ing the  broken  lines  as  representing  the  position  of  the  end  of  the 
coil  at  front  as  well  as  the  back  of  the  armature,  and  the  solid 
lines  as  simply  the  ends  of  the  wire  that  connect  with  the  com- 
mutator segments,  they  become  accurate  representations  of  coils 
of  any  number  of  turns. 

The  coils  of  multipolar  armatures  are  made  on  forms,  and  in 
the  finished  state  are  placed  upon  the  armature  core.  Some  coils 
are  so  formed  as  to  bend  down  over  the  ends  of  the  armature,  and 
are  then  given  the  form  at  the  ends,  shown  in  Fig.  64,  so  they 
may  fit  into  each  other.  In  some  machines,  the  coils  do  not  bend 
down  over  the  ends  of  the  armature,  but  run  out  parallel  with 
the  shaft.  Armatures  so  wound  are  sometimes  said  to  have  a 
barrel  winding,  and  the  coils,  if  laid  out  upon  a  flat  surface., 
would  present  the  appearance  of  Fig.  65  ;  that  is,  if  they  con- 


HANDBOOK    ON    ENGINEERING. 

abed 


45 


Fig.  64. 


Fig.  65. 


tained  more  than  one  turn.  If  of  the  single-turn  type,  they 
would  look  like  Fig.  66,  if  for  a  lap  winding;  and  like  Fig.  67, 
if  for  a  wave  winding,  the  ends  d  d  being  joined  and  then  con- 
nected with  the  commutator  segments. 

In  connecting    the   field    coils    of    multipolar    machines,  it   is 
necessary  to  be  careful  not  to  make  mistakes,  so  that  some  of  the 


/, 

\  V 

abc 

m 

\_              s 

\ 

ab  c 


ab 


d 

Fig.  67, 


46  HANDBOOK    ON    ENGINEERING. 

coils  will  act  to  magnetize  the  field  in  the  wrong  direction.  By 
studying  Fig.  27  and  the  explanation  of  it,  the  direction  of  the 
magnetic  lines  of  force  with  respcot  to  the  direction  of  the  current 
through  the  magnetizing  coils,  can  be  clearly  understood,  and 
then  there  will  be  no  difficulty  in  determining  the  proper  way  in 
which  to  connect  the  coil  ends,  for  all  we  have  to  do  is  to  make 
the  connections  such  that  if  one  pole  is  N  the  one  next  to  it  is  S. 
With  two-pole  machines,  it  is  also  necessary  to  be  careful  not  to 
connect  the  field  coils  improperly;  that  is,  if  there  is  more  than 
one  coil,  and  in  most  machines  this  is  the  case. 

The  current  that  energizes  a  magnet  is  called  the  magnetizing 
force  and  is  measured  in  ampere  turns.  The  ampere  turns  are 
obtained  by  multiplying  the  number  of  turns  of  wire  in  coil,  by 
the  amperes  of  current  flowing  through  it. 

All  forms  of  matter  resist  the  development  of  magnetic  force. 
This  resistance  is  called  magnetic  reluctance.  The  reluctance  of 
air  is  much  greater  than  that  of  iron  or  steel,  but  is  constant ; 
that  of  iron  and  steel  is  not.  If  one  thousand  ampere  turns 
develop  a  certain  magnetic  density  in  a  circuit  composed  wholly 
of  air,  two  thousand  ampere  turns  will  double  this  density.  In 
iron  and  steel  it  will  require  much  more  than  double  the  ampere 
turns  to  double  the  magnetic  density. 

If  in  a  magnetic  circuit  ten  inches  long,  100  ampere  turns 
develop  a  .certain  density,  it  will  require  200  ampere  turns  to 
develop  the  same  density  if  the  magnetic  circuit  is  double  the 
length.  The  table  on  page  209  gives  the  ampere  turns  required 
to  develop  different  magnetic  densities  in  magnetic  circuits  one 
inch  long,  composed  of  air,  iron  and  steel. 

To  find  ampere  turns  required  to  develop  any  magnetic  density 
in  any  magnet  use  following  rule :  — 

Multiply  the  figures  given  in  the  table  on  page  159  ;  for  density 
required,  by  length  of  the  magnetic  circuit,  and  the  product  will 
be  total  number  of  ampere  turns. 


HANDBOOK    ON    ENGINEERING.  47 


.CHAPTER     V. 

SWITCH-BOARDS,    DISTRIBUTING    CIRCUITS    AND   SWITCH- 
BOARD INSTRUflENTS. 

Generators  of  the  constant  potential  type  are  made  so  as  to 
develop  a  certain  voltage  at  a  given  velocity,  but  in  some  cases  it 
is  not  practicable  to  run  them  at  the  exact  speed  for  which  they 
are  designed ;  and  in  others,  it  is  desired  to  vary  the  voltage 
slightly,  hence,  all  machines  are  provided  with  means  for  chang- 
ing the  e.m.f.  slightly.  This  regulating  device  is  also  necessary 
in  cases  where  the  load  is  for  a  time  light,  and  for  the  balance  of 
the  time  heavy ;  for,  as  we  have  shown,  the  voltage  will  vary  to 
some  extent  with  changes  in  the  strength  of  the  current.  If 
the  generator  is  at  some  distance  from  the  points  where  the  cur- 
rent is  used,  the  drop  of  voltage  in  the  lines  will  be  greater  with 
strong  currents  ;  hence,  when  the  load  is  heavy,  it  is  necessary  to 
increase  the"  voltage  developed  by  the  generator.  As  it  is  not 
advisable  to  change  the  speed  of  the  engine,  the  variation  of  volt- 
age is  obtained  by  changing  the  strength  of  the  current  that 
flows  through  the  shunt  field  coils,  and  this  is  accomplished  by 
providing  a  resistance  that  can  be  cut  in  or  out  of  the  shunt  coil 
circuit,  as  is  illustrated  in  Fig.  68,  in  which  R  represents  the 
resistance,  or  field  regulator,  as  it  is  called.  When  the  lever  is 
moved  to  the  extreme  left  position,  all  the  regulator  resistance  is 
cut  out  of  the  circuit,  and  then  the  voltage  of  the  generator  is 
the  highest  that  can  be  obtained  with  the  speed  at  which  it  is  run- 
ning. When  the  lever  is  moved  to  the  extreme  right,  all  the 
resistance  of  the  regulator  is  introduced  into  the  shunt  coil  cir- 
cuit, and  then  the  voltage  is  the  lowest.  By  placing  the  lever  in 


48 


HANDBOOK    ON    ENGINEERING. 


intermediate  positions  between  the  extremes  right  HIK-!  left,  differ- 
ent voltages  may  be  obtained. 

To  be  able  to  operate  a  generator  furnishing  current  to  <»  sys- 
tem of  distributing  wires,  it   is   necessary    to    have    a  number  of 


(t 


d 


Fig.  68. 

instruments  and  other  devices,  included  in  the  circuit,  some  of 
which  are  absolutely  indispensable,  and  others  of  which  are  simply 
conveniences,  and  may  be  looked  upon  as  luxuries.  The  various 
devices  required  are  shown  in  Fig.  69.  The  generator  is  shown 
at  Jf,  and  at  e  the  field  regulator  is  placed,  audit  is  connected 
with  one  of  the  generator  armature  terminals  and  with  one  end 
of  the  shunt  coil  wires  by  means  of  wires  d  d.  The  wires  c  c 
run  from  the  generator  terminals  to  the  voltmeter  V,  and  thus 
enable  us  to  see  what  the  voltage  is  at  all  times.  Wires  a  and  b 
convey  the  current  to  the  external  circuit,  with  which  they  can  be 
connected  or  disconnected  by  means  of  switches  ,s.s-  *.s.  At  A  an 
ammeter  is  placed  which  indicates  the  strength  of  current  in 


HANDBOOK    ON    ENGINEERING. 


49 


amperes.  The  ammeter  can  be  placed  in  either  a  or  6,  as  the 
same  strength  current  Hows  in  both.  At// safety  fuses  are  pro- 
vided, so  as  to  open  the  circuit  in  case  the  current  becomes  so 
strong  as  to  be  capable  of  overheating  the  generator  wire.  If  one 
of  the  line  wires  runs  out  into  the  open  air,  and  is  carried  along  on 
poles,  we  will  have  to  provide  a  lightning  arrester,  as  shown  at  /i, 
this  being  connected  with  the  ground  as  at  g.  If  both  lines  run 
into  the  open  air,  an  arrester  must  be  placed  in  both ;  and  if 
both  are  confined  to  the  interior  of  a  building,  no  arresters  will 
be  required.  From  the  points  m  m  branch  circuits  may  be  run 
off  in  as  many  directions  as  necessary,  and  by  providing  switches 
s  s,  these  can  be  connected  or  disconnected  from  the  main  line 
when  desired. 

This  crude  arrangement  would  enable  us  to  operate  the  system 
successfully,  but  it  would  not  be  so  convenient  as  a  more  methodi- 


cal grouping  of  the  several  devices  and  instruments.  It  repre- 
sents the  way  things  were  done  in  the  early  days  of  electric  light- 
ing, but  at  the  present  time,  instead  of  having  the  several  parts 
scattered  about  in  a  helter-skelter  fashion,  they  are  all  assembled 

4 


50 


HANDBOOK    ON    ENGINEERING. 


upon  a  large  panel,  which  is  called  a  switch-board.  Fig.  70  gives 
the  general  arrangement  of  wiring  and  location  of  devices  for  a 
simple  board  arranged  for  one  generator  feeding  into  five  external 

\n      \P 


Fig.  70. 


circuits.  The  ammeter  and  voltmeter  are  placed  at  the  top  of  the 
board,  and  directly  under  these  are  arranged  five  switches,  s, 
which  control  the  external  circuits.  One  of  these  circuits  is  indi- 


HANDBOOK    ON    ENGINEERING.  51 

cated  by  the  lines  n  _p,  //,  being  safety  fuses.  The  wires  i  i  con- 
vey the  main  current  from  the  generator  to  a  circuit  breaker  Z>, 
which  is  simply  a  switch  that  is  constructed  so  that  it  will  open 
automatically  when  the  current  becomes  too  strong.  From  the 
circuit  breaker,  the  current  passes  through  wires  a  and  b  to  the 
main  switch  jP7,  and  by  wire  c,  it  runs  from  here  to  the  ammeter 
A  and  from  the  latter  by  wire  d  to  a  rod  1  which  is  called  a  bus 
bar.  The  upper  side  of  the  main  switch  is  connected  directly 
with  bus  2.  The  voltmeter  is  connected  with  two  busses  by  the 
wires  e  e.  The  field  regulator  is  located  back  of  the  board  at  72, 
and  is  connected  in  the  shunt  coil  circuit  by  means  of  wires  h  h. 
The  switch  of  the  regulator  R  is  connected  with  a  hand -wheel  on 
the  front  of  the  switch-board,  so  that  the  attendant  can  watch 
the  voltmeter  as  he  turns  the  wheel  and  thus  see  just  what  effect 
the  movement  is  producing  on  the  voltage. 

In  addition  to  the  devices  shown  in  Fig.  70,  we  can,  if  desired, 
provide  a  recording  ammeter,  a  recording  voltmeter  and  a  watt- 
meter ;  the  first  two  would  give  us  a  record  of  the  amperes  and 
volts  for  a  certain  length  of  time,  generally  24  hours,  and  the 
last  one  would  register  the  amount  of  electrical  energy.  We 
could  also  provide  ammeters  for  each  one  of  the  distributing  cir- 
cuits, so  as  to  know  the  strength  of  current  in  each  one. 

If  we  desire  to  arrange  the  switch-board  for  two  generators, 
and  these  are  of  the  shunt  type,  we  will  require  no  changes  in 
Fig.  70,  except  to  provide  another  regulator  and  a  main  switch 
and  circuit  breaker  for  the  additional  machine.  This  arrange- 
ment of  board  is  suitable  for  a  single  compound  wound  generator, 
or  any  number  of  shunt  wound  machines,  but  if  we  have  two  or 
more  compound  generators,  the  connections  between  these  and 
the  bus  bars  will  have  to  be  somewhat  modified. 

The  modifications  required  in  a  switch-board  for  two  or  more 
compound  generators  can  be  made  clear  by  the  aid  of  Figs.  71 
and  72.  In  the  first  figure,  we  can  see  that  if  the  current  return- 


52 


HANDBOOK    ON    ENGINEERING. 


ing  from  the  main  line  through  n  divides  into  wires  a  and  />,  it 
will  remain  divided  until  it  passes  through  the  armatures  and  the 
F  coils  of  the  two  machines,  and  thence  through  wires  <>  e,  it  will 


Fig.  71. 

reunite  again  in  wire  p.  In  Fig.  72,  the  two  parts  of  the  current 
will  flow  through  wires  d  d  to  the  single  wire  e,  and  then  divide 
into  wires//,  and  thus  reach  the  coils  F  F,  and.  finally,  through 
wires  h  /*,  reach  p.  In  Fig.  71,  if  the  right  side  armature  gen- 
erates more  current  than  the  other  one,  the  F  coil  of  that  gener- 
ator will  be  traversed  by  the  strongest  current,  for  in  each  machine 
the  strength  of  current  in  the  armature  and  the  F  coil  will  be 
nearly  the  same.  Now,  if  the  right  side  machine  generates  the 
strongest  current,  it  is  because  its  voltage  is  the  highest,  but  the 
fact  that  its  F  coil  will  be  traversed  by  the  strongest  current  will 
make  its  voltage  still  higher,  thus  increasing  the  difficulty.  In 
Fig.  72,  the  current  flowing  through  the  two  F  coils  will  be  the 
same,  no  matter  how  much  the  two  armature  currents  may  differ > 


HANDBOOK    ON    ENGINEERING.  53 

for  these  come  together  in  wire,  ^,  and  passing  from  this  to  the  two 
F  coils,  the  current  will  divide  in  equal  amounts.  As  can  be 
seen,  the  effect  of  adding  the  wires  d  <l,*e  and //'in  Fig.  f2  is  to 
equalize  the  currents  that  flow  through  the  F  coils,  and  thus  pre- 
vent, ;is  far  as  possible,  the  unequal  action  of  the  generators. 

When  two  or  more  compound  generators  are  connected  so 
as  to  feed  into  the  same  general  circuit,  the  connections  are 
made  in  accordance  with  Fig.  72.  Fig.  73  illustrates  a  switch- 
board for  two  compound  generators,  and,  as  will  be  noticed,  the 
most  striking  difference  between  it  and  Fig.  70,  is  that  there 
are  three  bus  bars  instead  of  two.  One  of  these  busses  is 
called  the  equalizer,  and  it  takes  the  place  of  wires  <1  d  <>  and 


//in  Fig.  72.  The  equalizing  connections  run  from  generator 
.vires /to the  main  switches  S,  and  thence  to  bus  1.  The  li  wires 
of  the  generators  run  to  one  side  of  the  circuit  breakers  D  E. 


54 


HANDBOOK    ON    ENGINEERING. 


and  thence  to  the  middle  blades  of  the  S  switches,  and  from  these 
to  the  bus  2.     The  generator  wires  run  to  the  outside   blades  of 


ff 


1 Li—I 


ff 


Fig.  73. 

the  circuit  breakers,  and  from  these  to  the  ammeters  A  A,  and 
thence  to  bus  3.  The  voltmeters  are  connected  with  wires  h  and 
/,  and  thus  indicate  the  e.m.f.'s  of  the  generators. 


HANDBOOK    ON    ENGINEERING.  55 

If  another  generator  were  added,  it  would  be  connected  with 
the  bus  bars  in  the  same  way. 

In  starting  two  or  more  compound-wound  generators,  one 
machine  is  started  first,  and  then  the  second  is  run  up  to  full 
speed,  and  its  voltage  is  adjusted  by  means  of  the  regulator  72,  so 
as  to  be  the  same  as  that  of  the  machine  that  is  running.  When 
the  voltages  of  the  two  machines  are  equal,  the  main  switch  of 
the  second  machine  is  closed  so  as  to  connect  it  with  the  bus  bars. 
This  action  will  generally  make  a  slight  change  in  the  voltage  of 
the  second  machine,  causing  it  to  run  up  or  down  a  trifle ;  and  as 
a  result  by  looking  at  the  ammeters,  we  will  find  that  it  is  taking 
more  or  less  than  its  share  of  the  load.  If  such  is  the  case,  we 
manipulate  the  regulator  R,  until  the  loads  are  properly  divided. 
Whether  the  voltage  of  the  second  machine  will  rise  or  fall  after 
it  is  connected  with  the  bus  bars,  will  depend  upon  the  extent  to 
which  it  is  compounded ;  if  slightly  compounded,  the  voltage  will 
drop,  and  if  heavily  compounded,  it  will  rise. 

The  switch-boards  illustrated  are  adapted  to  what  is  called  the 
two- wire  system  of  distribution,  but  in  cases  where  it  is  desired 
to  transmit  the  current  to  a  considerable  distance,  without  using 
extra  large  wire,  the  three- wire  system  of  distribution  is 
employed.  This  system  is  illustrated  in  Figs.  74  to  76. 

Suppose  we  have  two  generators  as  indicated  at  G  G  in  these 
diagrams,  and  let  the  direction  of  the  current  through  both  be 
from  bottom  toward  the  top ;  then  it  is  evident,  that  if  we  remove 
the  middle  wire  0,  the  lower  machine  will  deliver  current  into  the 
upper  one,  and  if  each  generator  develops  an  e.m.f.  of  115  volts, 
the  combined  e.m.f.  will  be  230  volts,  and  this  will  be  the 
pressure  between  the  bottom  and  top  wires;  but  the  voltage 
between  either  wire  and  the  center  one  will  only  be  115.  Suppose 
we  have  a  number  of  lamps  connected  between  wire  P  and  the 
center  wire  0,  and  an  equal  number  of  lamps  between  0  and  JV, 
as  is  shown  in  Fig.  74  ;  then  it  is  evident  that  the  same  amount 


56 


HANDBOOK    ON    ENGINEERING. 


of  current  will  flow  through  both  sets,  and  as  a  consequence,  all 
the  current  that  passes  from  the  upper  generator  into  wire  /•*  will 
go  directly  through  both  sets  of  lamps  to  the  lower  wire  N,  and 
thus  return  to  the  lower  side  of  the  bottom  generator.  Under 


these  conditions,  the -lamps  will  be  acted  upon  by  115  volts  each, 
but  the  current  will  be  driven  through  the  circuit  by  a  voltage  of 
230.  Now,  if  the  voltage  is  doubled,  four  times  the  number  of 
lamps  can  be  supplied  with  the  same  size  wires ;  hence,  the  cost 
of  line  wire  per  lamp  will  be  reduced  to  one-fourth.  Suppose, 
that  instead  of  having  the  lamps  equally  divided  as  in  Fig.  74, 


HANDBOOK    ON    ENGINEERING.  57 

they  are  arranged  as  in  Fig.  75  ;  then  since  the  current  fed  into 
the  system  from  the  upper  wire/3  is  only  sufficient  for  five  lamps; 
while  there  are  seven  lamps  in  the  lower  section,  it  follows  that 
through  wire  O  a  current  sufficient  for  two  lamps  must  be  sup- 
plied. The  way  in  which  the  currents  would  flow  in  this  case  is 
clearly  indicated  by  the  arrows. 

In  Fig.  74,  it  will  be  seen  that  if  we  removed  the  middle  wire, 
the  lamps  would  not  be  affected,  for  none  of  the  current  comes 
through  it;  but  in  Fig.  75,  if  we  cut  the  middle  wire,  two  of  the 
lower  lamps  would  be  unprovided  for.  From  this  it  will  be  seen 
that  the  object  of  the  middle  wire  is  simply  to  provide  the  extra 
current  required  for  the  side  that  carries  the  largest  number  of 
lamps.  If  the  lights  are  so  arranged  that  on  both  sides  of  the 
central  wire  0  the  number  is  practically  the  same  at  all  times, 
the  center  wire  can  be  made  very  small,  but  such  perfect  balance 
cannot  be  obtained  always,  and  on  that  accouut,  the  center,  or 
neutral  wire,  as  it  is  called,  is  made  of  the  same  size  as  the 
others,  except  in  large  systems,  in  which  it  is  sometimes  not  more 
than  one-third  the  size. 

As  motors  require  large  amounts  of  current,  they  are  nearly 
always  made  to  operate  with  a  voltage  of  230,  and  are  connected 
with  the  outside  wires  of  the  system,  as  is  shown  in  Fig.  76,  in 
which  a  a  a  a  and  c  c  c  c  indicate  lamps  connected  between  the 
sides  and  the  neutral  wire,  and  ABC  are  motors  connected 
across  the  outside  lines. 

When  a  switch- board  is  arranged  for  two  generators  connected 
with  a  three-wire  system,  we  use  three  bus  bars,  just  as  in  Fig. 
70,  but  discard  the  equalizing  connection,  and  connect  the 
generators  with  the  busses  in  the  same  way  as  they  are  connected 
with  wires  N  0  and  P  in  Figs.  74  to  76.  If  we  have  a  number  of 
generators  feeding  into  the  three-wire  system,  then  we  connect 
each  set  with  an  equalizer  bus;  that  is,  provide  two  sets  of 
busses,  and  the  P  and  N  busses  of  these  two  sets  we  connect 


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HANDBOOK    ON    ENGINEERING. 


with  a  third   set  in   the  proper  order  for  the   three-wire    system, 
and  from  the  latter  busses  the  external  circuits  are  fed. 

If  we  desire  to  supply  a  larger  building  with  a  lighting  and 
power  system,  we  can  run  the  wires  in  almost  any  way,  providing 
we  make  connections  with  the  lamps  and  motors,  but  if  we  adopt 


Fig.   77. 

a  systematic  arrangement  it  will  require  less  labor  to  operate  the 
plant,  and  when  anything  goes  wrong  we  will  be  able  to  locate 
the  difficulty  with  much  less  trouble  and  in  less  time.  The  best 
way  to  accomplish  this  is  by  the  use  of  small  switch-boards 
located  at  different  points  in  the  building,  these  becoming  centers 


HANDBOOK    ON    ENGINEERING.  59 

of  distribution,  from  which  all  the  lamps  are  supplied.  The 
general  arrangement  of  such  a  system  can  be  understood  from 
Fig.  77,  in  which  B  represents  the  main  switch-board,  located  in 
the  engine  room,  and  e  e  e  the  several  floors  upon  which  the  lights 
are  located.  From  the  main  switch-board  we  run  up  four  lines, 
one  to  each  floor,  and  locate  secondary  boards  at  C  0  and  D  D  D. 
We  can  also  run  out  lines  directly  from  the  board  to  the  lamp 
circuits  as  at  c  c  c  c.  From  the  boards  C  (7,  we  run  circuits  to 
smaller  boards,  as  shown  at  E,  F,  A,  A,  A,  and  b  b  b.  From 
each  one  of  these  small  boards  we  can  run  out  circuits  to  the 
lamps. 

These  small  switch-boards  are  called  panel  boards  or  boxes, 
and  also  distribution  boards.  They  are  made  of  all  sizes  from 
eight  or  ten  inches  square,  up  ^to  four  or  five  feet,  and  are 
arranged  to  feed  into  one  or  two,  or  fifty  or  sixty  circuits, 
supplying  anywhere  from  five  or  six  lights  up  to  a  thousand  or 
more. 

The  construction  of  distribution  boards  can  be  understood 
from  Figs.  78  and  79,  the  first  being  arranged  for  the  three- 
wire  system,  and  the  second  for  the  two- wire.  Fig.  78  is  ar- 
ranged to  feed  ten  circuits,  and  is  provided  with  one  main  switch 
by  means  of  which  the  entire  box  can  be  disconnected  from  the 
main  line.  The  distributing  circuits  are  provided  with  safety 
safety  fuses  on  the  outside  wires ,  so  that  if  anything  goes  wrong 
and  the  current  increases  to  a  dangerous  point,  the  circuit  will  be 
open.  No  fuse  is  placed  on  the  middle  wire,  as  it  is  not  neces- 
sary, and  might  result  in  cutting  out  both  sides  of  the  circuit 
when  only  one  was  disabled. 

Fig*  79  is  a  more  complete  panel,  because  each  one  of  the  six 
distribution  circuits  is  provided  with  0  switch,  so  that  it  is  pos- 
sible to  disconnect  any  of  the  circuits  without  interfering  with  the 
others.  In  some  cases  a  distribution  board  of  this  kind  is  the 
only  thing  that  will  answer  the  purpose,  but  in  others,  the  more 


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HANDBOOK    ON    ENGINEERING. 


simple  construction  of  Fig.  78  answers  just  us  well.  The  fuses 
in  Fig  78  are  shown  at  E  F.  These  fuses  are  sometimes  made  so 
that  they  can  be  used  as  switches  •  that  is,  they  can  be  pulled  out 


Fig.  78.  Fig.  79. 

of  place  and  thus  open  the  circuit,  and  if  one  blows  out  it  can  be 
removed  and  a  new  fuse  be  put  in,  and  then  it  can  be  replaced, 
thus  placing  the  disabled  circuit  in  service  without  interfering 
with  the  others. 

The  ammeters  uud.  voltmeters  used  on  switch-boards  depend 
for  their  operation  upon  the  repulsion  between  magnetic  lines  of 
force.  A  great  many  different  constructions  are  used,  but  most 
of  them  operate  upon  the  principles  illustrated  in  Fig.  80  or  81. 
If  a  small  bar  of  iron  c  is  placed  between  the  poles  of  a  permanent 
magnet,  as  in  Fig.  80,  it  will  be  held  in  the  horizontal  position  by 
the. attraction  of  the  magnet.  If  it  is  surrounded  by  a  stationary 
coil  of  wire  6,  through  which  a  current  of  electricity  passes,  then 


HANDBOOK    ON    ENGINEERING. 


61 


it  will  be  under  the  intlueiice  of  two  forces,  one  the  attraction  of 
the  poles  N  S  of  the  magnet,  and  the  other  the  attraction  of  the 
lines  of  foice  developed  by  the  current  flowing  through  coil  b. 
The  action  of  the  latter  will  tend  to  swing  the  rod  c  into  the  ver- 
tical position.  The  force  of  the  magnet  will  remain  constant,  but 
the  force  of  the  coil  will  vary  with  the  strength  of  the  current 
passing  through  it ;  hence,  the  stronger  the  current  the  more  the 
bar  c  will  be  swung  around  into  the  vertical  position.  If  we  pro- 
vide a  small  counter-weight,  as  shown  in  the  illustration,  to  resist 
the  action  of  the  coil,  we  will  have  a  means  that  will  enable  us  to 
adjust  the  movement  of  the  bar,  so  that  it  will  swing  around 
through  a  given  angle  for  a  given  increase  in  current.  If  a 
pointer  a  is  secured  to  c  it  will  swing  over  the  scale  as  shown, 
when  r  is  rotated  by  the  action  of  the  coil. 

If  coil  &  is  mounted  so  that  it  may  swing  around  the  center 
pivot,  we  can  discard  bar  c,  for  then  as  soon  as  a  current  traverses 
o,  the  lines  of  force  developed  around  it  will  be  attracted  by 


Fig.  80. 


Fig.  81. 


those  of  the  permanent  magnet,  and  will  exert  a  twisting  force  so 
as  to  place  the  axis  of  the  coil  parallel  with  the  lines  of  force 
passing  from  N  to  S.  In  this  case  as  in  the  previous  case,  the 


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HANDBOOK    ON    ENGINEERING. 


effort  to  twist  b  around  will  be  proportional  to  the  strength  of 
the  current,  hence,  the  stronger  the  current  the  greater  the 
swing.  Ammeters  and  voltmeters  are  made  on  these  principles, 
and  the  only  difference  in  the  two  instruments  is  in  the  size  of 
the  wire  used  for  the  coils. 

Figs*  82  and  83  illustrate  the  principle  upon  which  circuit 
breakers  are  made.  In  Fig.  82,  suppose  a  current  flows  through 
magnet  E,  then  it  will  attract  the  lever  A,  the  latter  being  made 


Fig.  82. 


Fig.  83. 


of  iron.  If  the  current  is  weak  it  may  not  develop  a  sufficient 
attractive  force  in  E  to  lift  the  weight  Z>,  and  in  that  case  A  will 
remain  where  it  is.  If,  however,  the  current  is  increased  until  E 
becomes  strong  enough  to  lift  /),  then  A  will  move  over  toward 
the  magnet,  and  the  catch  "  a  "  falling  behind  it,  will  not  allow 
it  to  return  to  its  former  position  until  placed  there  by  hand. 
When  A  swings  over,  it  carries  B,  and  thus  breaks  the  connec- 
tion with  (7  and  opens  the  circuit.  Thus  it  will  be  seen  that  by 
properly  adjusting  the  weight  D  and  the  magnet  E,  we  can  setthe 
device  so  as  to  open  the  circuit  whenever  the  current  reaches  a 
certain  strength.  This  is  the  principle  upon  which  circuit  break- 


HANDBOOK   ON   ENGINEERING.  63 

era  act,  but  such  a  device  as  Fig.  82  would  be  of  no  service  for 
lighting  circuits,  because  the  distance  by  which  C  and  B  are 
separated  is  too  small  to  break  the  current.  By  modifying  the 
construction  as  in  Fig.  83,  we  can  obtain  a  device  that  will  give  a 
wide  separation  at  the  breaking  point.  In  this  construction,  the 
lever  A  when  drawn  towards  the  magnet,  strikes  the  catch  a,  so 
as  to  release  lever  jB,  and  then  the  weight  D  throws  the  latter 
down  to  the  position  shown  in  broken  lines,  thus  giving  a  wide 
separation  between  F  and  C.  By  moving  the  weight  on  the  lower 
arm  at  A,  the  device  can  be  adjusted  so  as  to  act  with  different 
strengths  of  current. 

Circuit  breakers  as  actually  constructed,  do  not  have  the 
appearance  of  this  diagram,  but  they  operate  on  the  principle 
illustrated  by  it. 

The  electromotive  in  volts  force  developed  in  the  armature  of 
a  motor,  or  generator,  can  be  determined  if  we  know  the  number 
of  wires  upon  the  outer  surface,  the  number  of  maxwells  of  mag- 
netic flux  that  pass  through  the  armature  and  the  revolutions  per 
second.  The  rule  for  the  calculation  is  as  follows :  — 

Multiply  the  number  of  wires  on  the  outer  surface  of  the  arma- 
ture by  the  maxwells  of  magnetic  flux  and  by  the  revolutions  per 
second,  and  divide  this  product  by  100,000,000. 

This  is  the  rule  for  two  pole  armatures.  For  multipolar  arma- 
tures with  series,  or  wave  winding,  use  same  rule  making  the 
flux  equal  to  the  sum  of  the  fluxes  issuing  from  all  the  positive  poles. 

For  multipolar  armatures  with  a  lap,  or  parallel  winding,  use 
same  rule  but  take  the  flux  issuing  from  one  pole  only. 

To  obtain  the  pull  in  pounds  of  a  motor  armature  at  one  foot 
radius  use  the  following  rule :  — 

Multiply  the  number  of  wires  on  the  outer  surface  of  armature 
by  the  amperes  of  armature  current,  and  by  total  number  of  max- 
wells of  magnetic  flux  passing  through  armature,  and  divide  this 
product  by  852,000,000.  See  pages  13  and  46. 


64  HANDBOOK    ON    ENGINEERING. 


CHAPTER     VI. 
ELECTRIC  MOTORS. 

Motors  are  made  so  as  to  run  at  a  constant  velocity,  or  for 
variable  speed.  For  the  latter  type  of  machine,  the  field  coils  are 
wound  in  series,  and  for  constant  speed  the  shunt  winding  is  used. 
A  motor  of  either  kind  cannot  be  started  successfully  without 
placing  an  external  resistance  in  the  armature  circuit,  because, 
when  the  armature  is  at  a  standstill,  there  is  nothing  but  the 
resistance  of  the  wire  to  hold  the  current  back,  and  as  a  result,  if 
no  extra  resistance  is  provided,  the  first  rush  of  current  would  be 
very  great.  As  soon  as  the  armature  begins  to  revolve,  an  e.rn.f . 
is  induced  in  its  wires,  and  this  acts  in  opposition  to  the  e.m.f. 
of  the  line  current ;  that  is,  it  acts  like  a  back  pressure,  and  holds 
the  current  back.  On  this  account,  the  e.m.f.  of  a  motor  is 
called  a  counter  e.m.f.,  and  it  is  abbreviated  into  c. e.m.f. 

The  way  in  which  the  external  resistance  is  connected  with 
a  motor  is  illustrated  in  Fig.  84,  in  which  M  is  the  motor  and 
R  the  external  resistance.  I)  is  a  main  switch,  by  means  of 
which  the  motor  is  connected  with  the  main  line.  This  switch  is 
closed  first,  and  then  switch  F  is  moved  to  the  right  until  it  cov- 
ers the  first  contact  of  the  resistance  R.  The  current  can  then 
pass  directly  to  the  field  shunt  coils  through  wire  e,  and  thence  by 
wire  a,  return  to  the  main  line.  The  armature  current,  however, 
has  to  first  pass  through  the  resistance  J£,  before  it  can  reach  wire 
IT  and  thus  the  armature.  As  soon  as  the  armature  begins  to 
speed  up,  the  switch  F  is  advanced,  step  by  step,  and  in  a  few 
seconds  it  is  moved  to  the  extreme  right  position,  in  which  all  the 
resistance  R  is  cut  out  of  the  armature  circuit.  When  F  reaches 
this  position,  the  motor  should  be  running  at  full  speed. 


HANDBOOK    ON    ENGINEERING.  bO 

If  the  current  should  stop  while  the  motor  is  running,  the 
machine  would  stop,  also,  and  then,  if  the  current  were  turned 
on  again,  the  motor  would  be  caught  with  the  armature  connected 
across  the  line  without  an  external  resistance,  and  as  it  would  be 
at  a  standstill,  the  current  would  rise  to  an  enormous  strength. 
To  prevent  this,  the  switch  F  is  always  opened  whenever  the  motor 
stops.  The  attendant  may  forget  to  do  this,  however  ;  therefore 
automatic  switches  have  been  devised  that  will  open  themselves 
whenever  the  current  dies  out. 


Fig.   84 


A  simple  switch  provided  with  a  resistance  so  as  to  be  suited 
to  start  a  motor,  is  called  a  motor-starter,  and  one  that  in  addi- 
tion is  provided  with  means  for  automatically  flying  to  the  open 
position  whenever  the  current  fails,  is  called  an  automatic  under- 
load starter. 

If  the  motor  is  very  much  overloaded,  its  speed  will  slow  down 
and  the  current  will  increase  in  strength.  If  the  overload  is  suf- 
ficient, the  current  will  become  so  strong  as  to  be  able  to  ourn  out 

5 


66 


HANDBOOK    ON    ENGINEERING. 


the  armature  ;  hence,  it  is  desirable  to  provide  a  circuit  breaker 
that  will  open  the  circuit  when  the  current  becomes  so  strong  as 
to  be  liable  to  burn  out  the  machine.  Motor-starters  are  made 
with  a  circuit-breaking  attachment,  and  are  then  called  automatic 
overload  motor-starters.  A  device  that  combines  the  under  and 
overload  starter,  features  is  called  an  automatic  under  and  over- 
load starter,  and  by  some  people  it  is  called  a  "  no  voltage  "  and 
"  overload  starter." 

When  motors  were  first  introduced,  a  great  deal  of  trouble 
was  experienced  with  the  starters,  owing  to  the  fact  that  they 
were  arranged  so  that  when  the  motor  was  stopped,  the  connection 
with  the  field  coils  was  broken.  Now,  the  current  flowing  through 
the  field  coils  objects  to  stop  flowing  when  the  connection  is 
broken,  and,  consequently,  it  continues  to  flow  between  the  end  of 
switch  Fin  Fig.  84,  and  the  last  of  the  contacts  of  72,  until  the 
distance  is  more  than  the  e.m.f.  of  the  current  can  overcome. 


Fig.  85. 

This  action  produces  serious  sparking  at  the  last  terminal,  and  in 
addition,   produces   a    severe  strain    upon  the    insulation  of  the 


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67 


field  coils,  because,  as  the  current  is  headed  off  in  one  direction, 
it   tries  to  find    an    outlet    in    another.     This  action  is  what  is 


Fig.  86. 


commonly  called  the  "kick  of  the  motor  field."  All  this 
trouble  can  be  obviated  by  connecting  the  starter  with  the  motor 
in  such  a  way  that  the  field  circuit  is  never  opened,  as  is  shown 
in  Fig.  84.  As  this  is  quite  an  important  point,  I  will  present 
it  in  a  more  simple  form  in  Fig.  85,  in  which  it  will  be  seen  that 
the  field  coils  and  armature  are  permanently  connected,  so  that 
when  switch  &  opens  the  circuit,  the  field  current  can  flow  through 
the  armature,  until  it  dies  out.  All  first-class  concerns  make 
motor  starters  with  this  connection,  at  the  present  time.  Some 
of  them  add  the  curved  contact  e.  Without  this  contact,  it  can 
be  seen  that  when  the  switch  S  is  moved  to  the  top  position,  the 


68  HANDBOOK    ON     ENGINEERING. 

resistance  H  is  simply  transferred  from  the  armature  to  the  field 
circuit,  and  that  the  current  £oing  to  the  field  coils  has  to  pass 
through  this  resistance.  As  this  resistance  is  insignificant  in 
comparison  with  that  of  the  shunt  coils,  it  makes  little  difference 
whether  it  is  left  in  the  field  circuit  or  not,  but  by  the  addition  of 
e  it  can  be  cut  out. 

Variable  speed  motors  are  always  arranged  so  that  the  speed 
may  be  changed  by  hand  as  conditions  may  require.  Trolley-car 
motors  are  of  this  type,  and  so  are  the  motors  used  for  printing 
presses,  and  many  other  kinds  of  work.  Figs.  86  to  88  show 
arrangements  by  means  of  which  the  speed  may  be  varied  with 
series  wound  motors.  In  Fig.  86,  E  is  the  starting  box  and  F  is 
the  speed  regulator.  In  the  act  of  starting,  the  switches  are  in 
the  position  shown.  To  start,  the  switch  S  and  E  is  turned  so 
as  to  close  the  circuit  with  the  resistance  R  all  included.  S  is 
moved  toward  the  left  as  the  armature  speeds  up,  and  reaches 
the  last  position  when  full' speed  is  attained.  If  the  switch  of  F 
is  now  closed,  a  portion  of  the  current 'will  be  diverted  from  the 
armature,  and  thus  its  rotating  force  will  be  reduced,  and  thereby 
its  speed.  This  method  of  speed  control  is  also  arranged  so 
that  the  two  switches  act  together,  so  as  to  introduce  resistance 
into  the  motor  circuit,  and  at  the  same  time  divert  more  or  less 
of  the  current  around  the  armature.  It  is  not  used  extensively, 
as  all  the  current  that  passes  through  F  is  just  so  much  thrown 
away. 

In  Fig.  87  the  speed  is  controlled  by  means  of  the  switch  F, ' 
which  cuts  out  portions  of  the  field  coils  and  this  changes  the 
strength  of  the  field.  With  this  arrangement,  if  a  portion  of 
the  field  is  cut  out,  the  motor  will  run  faster,  because  the  c.e.m.f 
will  be  reduced,  therefore,  the  armature  current  will  be  increased. 
To  obtain  a  wide^  range  of  regulation,  it  is  necessary  to  wind  a 
large  number  of  turns  of  wire  on  the  field,  so  that  with  all  the 
wire  in  service,  the  speed  may  be  the  lowest  required. 


HANDBOOK    O"N     ION(J  INKKRING. 


69 


Fig.  88  shows  another  arrangement  that  varies  the  strength  of 
the  field  by  diverting  a  portion  of  the  current  through  switch  F. 
It  gives  as  wide  a  range  of  regulation  as  Fig.  87,  but  is  not  so 
economical. 

Figs-  86  and  88  cannot  be  used  to  regulate  the  speed  of  shunt 
motors,  but  Fig.  87  can.  The  first  two  named  figures,  if  used 


Fig.   87. 

with  a  shunt  motor,  would  simply  afford  a  third  path  through 
which  current  could  pass  from  one  side  of  line  to  the  other,  that 
is,  from  the  p  to  the  n  wires,  but  this  would  not  materially  affect 
the  strength  of  current  that  would  flow  through  the  armature  and 
field  coils.  They  work  with  series  wound  motors,  because  the 
current  is  not  shunted  from  wire  p  to  wire  n  but  simply  from 
one  side  of  the  armature,  or  the  field,  to  the  other. 


70 


HANDBOOK    ON    ENGINEERING. 


Fig,  89  shows    an  arrangement    by   means    of    which    a    shunt 
motor  can  be  made  for  variable  speed.      In   this   case,    the  switch 


Fig.   88. 

and  resistance  E  is  simply  an  ordinary  starter,  and  F  is  a  resist- 
ance that  is  introduced  in  the  field  circuit,  so  as  to  vary  the 
strength  of  the  field.  With  this  arrangement  the  slowest  speed  is 
obtained  when  all  the  resistance  of  F  is  out  of  the  circuit. 

The  direction  in  which  a  motor  runs  can  be  reversed  by  sim- 
ply reversing  the  direction  of  the  current  through  the  armature. 
Any  of  the  arrangements  for  varying  the  speed  can  be  used  in 
connection  with  reversible  motors  by  arranging  the  switch  so  as 


HANDBOOK    OX    ENGINEE&ING. 


71 


to  reverse  the  armature  connections.  Fig.  (.»0  will  give  a  fail- 
idea  of  the  \v:iy  in  which  :i  reversing  switcli  is  made.  This  repre- 
sents the  type  of  switch  used  most  generally  for  this  purpose,  and 
it  is  known  as  the  cylinder  switch.  It  is  the  kind  used  on  trol- 
ley-cars. The  vertical  row  of  circles  numbered  from  one  to 
eleven  represents  stationary  contact  pieces,  to  which  the  terminals 
of  the  motor,  the  line  and  the,  resistance  are  attached.  The 
shaded  parts  1>  7J  are  metal  plates  that  are  secured  to  the 
surface  of  a  cylinder,  that  is  so  located  that  as  it  is  turned  in  one 
direction  or  the  other,  these  plates  slide  over  the  stationary  con- 
tacts. If  the  cylinder  is  turned  so  that  the  plates  on  the  right 
side  slide  over  the  contacts,  the  motor  will  run  in  one  direction, 
and  if  the  cylinder  is  turned  in  the  other  direction,  the  motor  will 
be  reversed.  Suppose  the  right  side  plates  slide  over  the  con- 


Fig.  89. 

tacts,  then  the  current  f rom  p  will  pass  to  contact  2,  and  thence 
to  wire  «,  and  to  the  left-side  of  the  field.  Through  wire  d  it 
will  return  from  the  field  to  contact  5,  and  by  means  of 


12  HANDBOOK    ON    ENGINEERING. 

plates  J^and  T7,  which  are  connected  as  shown  at  X1,  it  will  reach 
contact  3  atid  wire  6,  which  runs  to  the  lower  side  of  the  arma- 
ture. From  the  top  of  the  armature,  through  wire  c,  the  current 
will  return  to  contact  4  and  through  plates  S  and  M  and  the  con- 
nection X  will  reach  contact  6 ,  which  by  one  of  the  wires  e  con- 


Fig.  90. 

nects  with  the  left-side  of  the  resistance  D.  From  the  right-side 
of  this  resistance,  the  current  will  pass  to  contact  10,  and  thus 
to  contact  11,  through  the  cylinder  plate,  and  in  that  way  reach 
line  wire  n. 

If  the  cylinder  is  turned  further  around,  contact  7  will  be  cov- 
ered by  plate  M,  and  this  will  cut  one  section  of  D.     By  a  further 


HANDBOOK    ON    ENGINEERING.  73 

movement,  contact  8  will  be  covered,  thus  cutting  out  another 
section,  and  by  continuing  the  movement,  all  of  D  can  be  cut  out. 

If  the  cylinder  is  turned  so  as  to  slide  the  left-side  plates  over 
the  contacts,  the  change  effected  will  be  that  contact  5  will  be 
connected  with  4  instead  of  with  3,  and  contact  6  will  be  con- 
nected with  3  instead  of  4,  thus  reversing  the  direction  of  the 
current  through  the  armature. 

The  strength  of  an  electric  current  is  measured  in  amperes. 
The  electromotive  force  that  drives  an  electric  current  through  a 
circuit  is  measured  in  volts.  The  resistance  that  a  wire  or  other 
circuit  offers  to  the  passage  of  an  electric  current  through  it  is 
measured  in  ohms. 

The  unit  of  resistance,  the  Ohm,  is  the  resistance  oi  a  column 
of  mercury  about  40  inches  long  and  about  five  hundredths  of  an 
inch  in  diameter,  or,  to  be  more  exact,  106  centimeters  long,  and 
one  millimeter  in  diameter. 

THE  WATT. 

The  watt  is  the  unit  of  electric  power — the  volt  ampere,  the 
power  developed,  and  is  equal  to  TJg-  of  one  horse  power.  A  con- 
venient multiple  of  this  is  called  the  Kilowatt,  written  K.  W.,  and 
is  equal  to  1,000  watts. 

THE  AflPERE. 

The  ampere  is  the  practical  unit  of  electric  current,  such  a  cur- 
rent [or  rate  of  flow,  or  transmission  of  electricity]  as  would 
pass,  with  an  electromotive  force  of  one  volt,  through  a  circuit 
whose  resistance  is  equal  to  one  ohm  ;  a  current  of  such  a  strength 
as  would  deposit  from  solution  .006084  grains  of  copper  per 

second. 

CANDLE  POWER. 

The  candle  power  is  the  unit  of  light ;  and  a  standard  candle 
is  a  candle  of  definite  composition  which  with  a  given  consump- 
tion in  a  given  time,  will  produce  a  light  of  a  fixed  and  definite 
brightness.  A  candle  which  burns  120  grains  of  spermaceti  wax 
per  hour,  or  two  grains  per  minute,  will  give  an  illumination 
equal  to  one  standard  candle. 


74  HANDBOOK    ON -ENGINEERING. 


CHAPTER    VII. 

INSTRUCTIONS  FOR  INSTALLING  AND  OPERATING  SLOW  AND 
MODERATE  SPEED  GENERATORS  AND  HOTORS. 

To  remove  the  armature,  take  off  the  brush-holders,  brush 
yoke,  pulley  and  bearing  caps  and  put  a  sling  on  the  armature,  as 
shown  in  accompanying  illustration.  A  spreader  of  suitable 
length  should  be  used  and  its  location  adjusted  to  prevent  the 
rope  from  drawing  against  the  flange  or  end  connections. 

In  assembling,  marked  parts  of  the  machine  should  be  assem- 
bled strictly  according  to  the  marking.  Clean  all  connection 
joints  carefully  before  clamping  them  together.  Wipe  the  shaft- 
bearing  sleeves  and  oil  cellars  perfectly  clean  and  free  from  grit. 
Place  the  bearing  sleeves  and  oil  rings  in  position  on  the  shaft 
and  then  lower  the  armature  into  place,  taking  care  that  the  oil 
rings  are  not  jammed  or  sprung.  As  soon  as  the  armature  is  in 
position,  pour  a  little  oil  in  the  bearing  sleeves,  put  the  caps  on 
the  boxes  and  screw  them  down  snugly.  The  top  field  should 
next  be  put  on  and  bolted  firmly  into  position,  and  a  level  placed 
on  the  shaft  to  check  the  leveling  of  the  foundation. 

Fill  the  bearings  with  the  best  grade  of  thin  lubricating  oil  and 
do  not  allow  it  to  overflow.  Oil  throwing  is  usually  due  to  an 
excess  of  oil  and  can  be  avoided  by  care  in  filling  the  oil  cellars. 

To  complete  the  assembly,  place  the  pulley  on  the  shaft,  draw 
up  the  set  screws  and  put  on  the  brush  rigging  and  connection 
blocks. 

STARTING. 

Before  putting  on  the  belt,  see  that  all  screws  and  nuts  are 
tight  and  turn  the  armature  by  hand  to  see  that  it  is  free  and 


HANDBOOK    ON    ENGINEERING.  75 

does  not  rub  or  bind  at  any  point.  Pat  on  the  belt  with  the 
machine  so  placed  on  the  rails  as  to  have  the  minimum  distance 
between  pulley  centers.  Start  the  machine  up  slowly  and  see 
that  the  oil  rings  in  bearings  are  in  motion.  As  the  machine 


comes  up  to  speed,  tighten  the  belt  till  it  runs  smoothly,  and  run 
the  machine  long  enough  without  load  to  make  sure  that  the  bear- 
ings are  in  perfect  condition.  The  bearings,  when  running, 
should  be  examined  at  least  once  a  week. 


CARE  OF  COMMUTATOR. 

The  commutator  brushes  and  brush-holders  should  at  all 
times  be  kept  perfectly  clean  and  free  from  carbon  or  other  dust. 
Wipe  the  commutator  from  time  to  time  with  a  piece  of  canvas 
lightly  coated  with  vaseline.  Lubricant  of  any  kind  should  be 
applied  very  sparingly. 


76  HANDBOOK    ON   ENGINEERING. 

t  \ 

If  a  commutator  when  set  up  begins  to  give  trouble  by  rough- 
ness, with  attendant  sparking  and  excessive  heating,  it  is  neces- 
sary to  immediately  take  measures  to  smooth  the  surface.  Any 
delay  will  aggravate  the  trouble,  and  eventually  cause  high  tem- 
peratures, throwing  off  solder,  and  possibly  displacement  of  the 
segments.  No.  0  sandpaper,  fitted  to  a  segment  of  wood,  with  a 
radius  equal  to  that  of  the  commutator,  if  applied  in  time  to  the 
surface  when  running  at  full  speed  (and  if  possible  with  brushes 
raised),  and  kept  moving  laterally  back  and  forth  on  the  commu- 
tator, will  usually  remedy  the  fault. 


DIRECTIONS  FOR  STARTING  DYNAMOS. 

GeneraL  —  Make  sure  that  the  machine  is  clean  throughout, 
especially  the  commutator,  brushes,  electrical  connections,  etc. 
Remove  any  metal  dust,  as  it  is  very  likely  to  make  a  ground  or 
short  circuit. 

Examine  the  entire  machine  carefully,  and  see  that] there  are 
no  screws  or  other  parts  that  are  loose  or  out  of  place.  See  that 
the  oil-cups  have  a  sufficient  supply  of  oil,  and  that  the  passages 
for  the  oil  are  clean  and  the  feed  is  at  the  proper  rate.  In  the 
case  of  self -oiling  bearings,  see  that  the  rings  or  other  means  for 
carrying  the  oil  work  freely.  See  that  the  belt  is  in  place  and 
has  the  proper  tension.  If  it  is  the  first  time  the  machine  is 
started,  it  should  be  turned  a  few  times  by  hand,  or  very  slowly, 
in  order  to  see  if  the  shaft  revolves  easily  and  the  belt  runs  in 
center  of  pulleys. 

The  brushes  should  now  be  carefully  examined  and  adjusted 
to  make  good  contact  with  the  commutator  and  at  the  proper 
point,  the  switches  connecting  the  machine  to  the  circuit  being 
left  open.  The  machine  should  then  be  started  with  care  and 
brought  up  to  full  speed,  gradually  if  possible ;  and  in  any  case 


HANDBOOK    ON    ENGINEEKING.  77 

the  person  who  starts  either  a  dynamo  or  a  motor  should  closely 
watch  the  machine  and  everything  connected  with  it,  and  be  ready 
to  throw  it  out  of  circuit  if  it  is  connected,  and  shut  down  and 
stop  it  instantly  if  the  least  thing  seems  to  be  wrong,  and  should 
then  be  sure  to  find  out  and  correct  the  trouble  before  starting 
again. 

STARTING  A  DYNAMO. 

In  the  case  of  a  dynamo  it  is  usually  brought  up  to  speed 
either  by  starting  up  a  steam-engine  or  by  connecting  the 
dynamo  to  a  source  of  power  already  in  motion.  The  former 
should,  of  course,  only  be  attempted  by  a  person  competent  to 
manage  steam-engines  and  familiar  with  the  particular  type  in 
question.  This  requires  special  knowledge  acquired  by  experi- 
ence, as  there  are  many  points  to  appreciate  and  attend  to,  the 
neglect  of  any  of  which  might  cause  serious  trouble.  For  ex- 
ample, the  presence  of  water  in  the  cylinder  might  knock  out  the 
cylinder-head  ;  the  failure  to  set  the  feed  of  the  oil-cups  properly 
might  cause  the  piston-rod,  shaft,  or  other  part,  to  cut.  And 
other  great  or  small  damage  might  be  done  by  ignorance  or  care- 
lessness. The  mere  mechanical  connecting  of  a  dynamo  to  a 
source  of  power  is  usually  not  very  difficult;  nevertheless,  it 
should  be  done  carefully  and  intelligently,  even  if  it  only  requires 
throwing  in  a  friction-clutch  or  shifting  a  belt  from  a  loose  pul- 
ley. To  put  a  belt  on  a  pulley  in  motion  is  difficult  and  danger- 
ous, particularly  if  the  belt  is  large  or  the  speed  is  high,  and 
should  not  be  tried  except  by  a  person  who  knows  just  how  to  do 
it.  Even  if  a  stick  is  used  for  this  purpose,  it  is  apt  to  be  caught 
and  thrown  around  by  the  machinery,  unless  it  is  used  in  exactly 
the  right  way. 

It  has  been  customary  to  bring  dynamos  to  full  speed  before 
the  brushes  are  lowered  into  contact  with  the  commutator ;  but 


78  HANDBOOK    ON    ENGINEERING. 

this  is  not  necessary,  provided  the  dynamo  is  not  allowed  to  turn 
backwards,  which  sometimes  occurs  from  carelessness  in  starting, 
and  might  injure  copper  brushes  by  causing  them  to  catch  in  the 
commutator.  If  the  brushes  are  put  in  contact  before  starting, 
they  can  be  more  easily  and  perfectly  adjusted  and  the  e.m.f . 
will  come  up  slowly,  so  that  any  fault  or  difficulty  will  develop 
gradually  and  can  be  corrected ;  or  the  machine  can  be  stopped, 
before  any  injury  is  done  to  it  or  to  the  system.  In  fact,  if  the 
machine  is  working  alone  on  a  system,  and  is  absolutely  free  from 
any  danger  of  short-circuiting  any  other  machine  or  storage  bat- 
tery on  the  same  circuit,  it  may  be  started  while  connected  to  the 
circuit,  but  not  otherwise.  If  there  are  a  large  number  of  lamps 
connected  in  the  circuit,  the  field  magnetism  and  voltage  might 
not  be  able  to  "  build  up  "  until  the  line  is  disconnected  an 
instant. 

If  one  dynamo  is  to  be  connected  with  another,  or  to  a  circuit 
having  other  dynamos  or  a  storage  battery  working  upon  it,  the 
greatest  care  should  be  taken.  This  coupling  together  of 
dynamos  can  be  done  perfectly,  however,  if  the  correct  method  is 
followed,  but  is  likely  to  cause  serious  trouble  if  any  mistake  is 
made. 

SWITCHING  DYNAHOS  INTO  CIRCUIT. 

Two  or  more  machines  are  often  connected  to  a  common  cir- 
cuit. This  is  especially  the  case  in  large  buildings  where  the 
number  of  lamps  required  to  be  fed  varies  so  much  that  one 
dynamo  may  be  sufficient  for  certain  hours,  but  two,  three  or 
more  machines  may  be  required  at  other  times.  The  various 
ways  in  which  this  is  done  depending  upon  the  character  of  the 
machines  and  of  the  circuit  and  the  precautions  necessary  in 
each  case  make  this  a  most  important  and  interesting  subject, 
which  requires  careful  consideration. 

Dynamos  may  be  connected  together  either  in  parallel  (mul- 
tiple arc)  or  in  series. 


HANDBOOK    ON    ENGINEERING.  79 


DYNAMOS  IN  PARALLEL. 

In  this  case  the  +  terminals  are  connected  together  or  to  the 
same  line,  and  the  —  terminals  are  connected  together  or  to  the 
other  line.  The  currents  (i.  e.  amperes)  of  the  machines  are 
thereby  added,  but  the  e.m.f.  (volts)  are  not  increased.  The 
chief  condition  for  the  running  of  dynamos  in  parallel  is  that 
$heir  voltages  shall  be  equal,  but  their  current  capacities  may  be 
different.  For  example:  A  dynamo  producing  10  amperes  may 
be  connected  to  another  generating  100  amperes,  provided  the 
voltages  agree.  Parallel  working  is,  therefore,  suited  to  constant 
potential  circuits.  A  dynamo  to  be  connected  in  parallel  with 
others  or  with  a  storage  battery,  must  first  be  brought  up  to  its 
proper  speed,  e.m.f.,  and  other  working  conditions,  otherwise, 
it  will  short-circuit  the  system,  and  probably  burn  out  its 
armature.  Its  field  magnetism  must,  therefore,  be  at  full 
strength,  owing  to  the  fact  that  it  generates  no  e.m.f.  with 
no  field  magnetism.  Hence,  it  is  well  to  find  whether  the  pole 
pieces  are  strongly  magnetized  by  testing  them  with  a  piece  of 
iron,  and  to  make  sure  of  the  proper  working  of  the  machine  in 
all  other  respects  before  connecting  the  armature  to  the  circuit. 
It  is  a  common  accident  for  the  field-circuit  to  be  open  at  some 
point,  and  thus  cause  very  serious  results.  In  fact,  a  dynamo 
should  not  be  connected  to  a  circuit  in  parallel  with  others  until 
its  voltage  has  been  tested  and  found  to  be  equal  to,  or  slightly 
(not  over  1  or  2  per  cent)  greater  than  that  of  the  circuit.  If  the 
voltage  of  the  dynamo  is  less  than  that  of  the  circuit,  the  current 
will  flow  back  into  the  dynamo  and  cause  it  to  be  run  as  a  motor. 
The  direction  of  rotation  is  the  same,  however,  if  it  is  shunt- 
wound,  and  no  great  harm  results  from  a  slight  difference  of 
potential.  But  a  compound-wound  machine  requires  more  careful 
handling. 


80  HANDBOOK    ON    ENGINEERING. 


DIRECTIONS  FOR  RUNNING  DYNAMOS  AND  MOTORS. 

In  the  case  of  a  machine  which  has  not  been  run  before,  or 
has  been  changed  in  any  way,  it  is  of  course  wise  to  watch  it 
closely  at  first.  It  is  also  well  to  give  the  bearings  of  a  new 
machine  plenty  of  oil  at  first,  but  not  enough  to  run  on  the  arma- 
ture, commutator  or  any  part  that  would  be  injured  by  it,  and 
to  run  the  belt  rather  slack  until  the  bearings  and  belt  have  got- 
ten into  easy  working  condition.  If  possible  a  new  machine 
should  be  run  without  load  or  with  a  light  one  for  an  hour  or 
two,  or  several  hours  in  the  case  of  a  large  machine ;  and  it  is 
always  wrong  to  start  a  new  machine  with  its  full  load,  or  even  a 
large  fraction  of  it.  ** 

This  is  true  even  if  the  machine  has  been  fully  tested  by  its 
manufacturer  and  is  in  perfect  condition,  because  there  may  be 
some  fault  in  setting  'it  up,  or  some  other  circumstance  which 
would  cause  trouble.  All  machinery  requires  some  adjust- 
ment and  care  for  a  certain  time  to  get  it  into  smooth  working 
order. 

When  this  condition  is  reached,  the  only  attention  required 
is  to  supply  oil  when  needed,  keep  the  machine  clean  and  see 
that  it  is  not  overloaded.  A  dynamo  requires  that  its  voltage  or 
current  should  be  observed  and  regulated  if  it  varies.  The  per- 
son in  charge  should  always  be  ready  and  sure  to  detect  the 
beginning  of  any  trouble,  such  as  sparking,  the  heating  of  any 
part  of  the  machine,  noise,  abnormally  high  or  low  speed,  etc. ; 
before  any  injury  is  caused,  and  to  overcome  it  by  following 
directions  given  elsewhere.  Those  directions  should  be  pretty 
thoroughly  committed  to  mind,  in  order  -to  facilitate  the  prompt 
detection  and  remedy  of  any  trouble  when  it  suddenly  occurs,  as 
is  apt  to  be  the  case.  If  possible,  the  machine  should  be  shut 


HANDBOOK    ON    ENGINEERING.  81 

down  instantly  when  any  trouble  or  indication  of  one  appears,  in 
order  to  avoid  injury  and  give  time  for  examination. 

Keep  all  tools  or  pieces  of  iron  or  steel  away  from  the  machine 
while  running,  as  they  might  be  drawn  in  by  the  magnetism,  and 
perhaps  get  between  the  armature  and  pole-pieces  and  ruin  the 
machine.  For  this  reason,  use  a  zinc,  brass  or  copper  oil-can 
instead  of  iron  or  v'  tin  "  (tinned  iron). 

Particular  attention  and  care  should  be  given  to  the  commu- 
tator and  brushes  to  see  that  the  former  keeps  perfectly  smooth 
and  that  the  latter  are  in  proper  adjustment.  (See  Sparking.) 

Never  lift  a  brush  while  the  machine  is  delivering  current, 
unless  there  are  one  or  more  other  brushes  on  the  same  side  to 
carry  the  current,  as  the  spark  might  make  a  bad  burnt  spot  on 
the  commutator. 

Touch  the  bearing's  and  field-coils  occasionally  to  see  that 
they  are  not  hot.  To  determine  whether  the  armature  is  running 
hot,  place  the  hand  in  the  current  of  air  thrown  out  from  it  by 
centrifugal  force. 

Special  care  should  be  observed  by  any  one  who  runs  a  dynamo 
or  motor  to  avoid  overloading  it,  because  this  is  the  cause  of  most 
of  the  troubles  which  occur. 


rjfcY,     OF  THE 
UNIVERSITY  j 

>^ 


82  HANDBOOK    ON    ENGINEERING. 


CHAPTER    VIII. 

WHY  COMMUTATOR  BRUSHES  SPARK  AND  WHY  THEY  DO 

NOT  SPARK. 

I  might  give  a  long  list  of  reasons  why  commutator  brushes 
spark,  and  why  they  do  not  spark,  but  by  such  a  procedure  no 
light  would  be  thrown  on  the  subject,  because  the  reasons  would 
not  be  understood  unless  fully  explained.  I  therefore  propose  to 
explain  the  subject  and  let  the  reader  tabulate  the  reasons  after 
digesting  the  explanation  of  the  principles  involved. 

Whenever  an  electric  current  is  interrupted,  a  spark  is  pro- 
duced and  it  makes  no  difference  how  the  current  is  generated, 
or  what  kind  of  a  conductor  it  is  flowing  through.  To  break 
a  current  without  a  spark  is  not  a  possibility ;  hence,  if  we 
desire  to  open  a  circuit  without  producing  a  spark,  the  only  way 
to  accomplish  the  result  is  by  killing  the  current  before  the 
circuit  is  opened.  The  brushes  resting  on  the  commutator  of  a 
motor  or  a  generator  have  to  transmit  to  the  armature  and  take 
away  from  it  the  current  that  is  generated,  in  the  case  of  a 
generator,  or  the  current  that  drives  the  machine  in  the  case  of  a 
motor.  If  the  brushes  were  made  so  narrow  that  they  could  only 
make  contact  with  one  commutator  segment  at  a  time,  it  would 
be  impossible  to  run  the  machine  without  producing  very  destruc- 
tive sparks.  Commutators,  however,  are  not  made  in  this  way. 
The  insulation  between  the  segments  is  narrow,  and  the  brushes 
are  wide  enough  to  be  always  in  contact  with  two  segments,  and 
part  of  the  time  with  three.  Suppose  that  the  proportions  are 
such  that  during  most  of  the  time  the  brush  only  touches  two 


HANDBOOK    ON    ENGINEERING.  83 

segments,  as  shown  in  Fig.  1.  With  these  proportions  it  will  be 
seen,  that  so  long  as  there  are  two  segments  in  contact  with  each 
brush,  it  is  a  possibility  *or  the  current  to  be  diverted  through 
one  of  them  only.  Suppose  that  at  the  instant  when  the  forward 
segment  is  passing  from  under  the  brush,  all  the  current  .flows 
through  -the  rear  segment ;  then  it  is  quite  evident  that  the  first- 
named  segment  will  break  away  from  contact  with  the  brush  with- 
out making  a  spark,  for  there  will  be  no  current  flowing  from  it 
to  the  brush. 

All  the  foregoing  is  self-evident,  but  it  will  be  suggested  that 
although  the  brush  can  break  away  from  the  front  segment  with- 
out producing  a  spark,  it  cannot  do  the  same  thing  with  the  rear 
segment,  for  all  the  current  is  flowing  through  this  one.  While 
it  is  true  that  when  the  forward  segment  passed  from  under  the 
brush  all  the  current  was  flowing  through  the  rear  segment,  it  is 
not  true  that  the  current  continues  to  follow  this  path.  As  soon 
as  the  front  segment  passes  from  under  the  brush,  the  rear  one 
becomes  the  forward  segment,  and  while  it  is  advancing  to  the 
point  where  it  must  pass  from  under  the  brush,  the  current  can 
be  transferred  to  the  next  segment  back  of  it  which  now  plays 
the  part  of  rear  segment.  Thus  we  see  that  to  be  able  to  run  a 
machine  without  producing  sparks  at  the  commutator,  all  we  have 
to  do  is  to  provide  means  whereby  the  current  is  transferred  from 
one  segment  to  the  one  back  of  it  as  the  commutator  revolves,  so 
that  when  the  segments  pass  from  under  the  brush  there  is  no 
current  flowing  through  them.  This  result  is  accomplished  more 
or  less  perfectly  in  all  machines,  made  by  responsible  firms. 
There  are  machines  on  the  market  that  have  been  designed  by 
men  that  are  not  well  enough  posted  in  the  principles  of  electrical 
science  to  obtain  proper  proportions,  and  these  are  not  propor- 
tioned so  as  to  shift  the  current  from  the  forward  to  the  rear 
segment  as  fast  as  the  machine  revolves ;  such  machines  always 
produce  more  or  less  serious  sparking. 


84  HANDBOOK    ON    ENGINEERING. 

If  a  machine  is  accurately  made  and  the  armature  coils  and 
commutator  segments  are  properly  spaced  and  sufficient  in  num- 
ber, it  is  possible  to  get  the  brushes  so  there  will  be  little  or  no 
spark  at  a  given  load  ;  but  if  the  current  strength  be  increased  or 
reduced,  the  sparks  will  appear,  and  the  more  the  current  is 
changed  the  larger  the  sparks  will  be,  the  increasing'  current 
producing  the  greatest  sparking. 

The  way  in  which  the  current  is  shifted  from  the  front  to  the 
rear  segment  I  will  explain  in  connection  with  Fig.  1.  In  this 
figure,  A  represents  a  portion  of  the  core  of  a  ring  armature. 
The  shaft  upon  which  it  is  mounted  is  shown  at  D,  and  P  N  are 
the  corners  of  the  poles  between  which  it  rotates.  The  small 
blocks  C  represent  a  portion  of  the  commutator  segments,  which 
we  have  placed  outside  of  the  armature,  so  as  to  make  the  diagram 
as  simple  as  possible.  For  the  same  reason  I  have  shown  the 
armature  coils  as  made  of  two  turns  of  wire  each.  The  line  F 
divides  the  space  between  the  ends  of  the  poles  into  two  equal 
parts,  and  the  line  E  divides  the  armature  into  two  halves 
on  which  the  directions  of  the  induced  currents  is  opposite.  In 
all  the  coils  to  the  right  of  line  E  the  currents  are  induced  in 
a  direction  away  from  the  shaft,  and  in  all  the  coils  to  the  left 
of  line  E  the  currents  flow  toward  the  shaft,  all  of  which  is 
clearly  indicated  by  the  arrow  heads  placed  upon  the  lines  repre- 
senting the  coils.  The  outline  B  represents  the  end  of  one  of  the 
brushes,  and  from  the  direction  in  which  it  is  inclined  it  will  be 
understood  that  the  armature  revolves  in  a  direction  counter  to 
that  of  the  hands  of  a  clock. 

When  the  armature  is  in  the  position  shown,  the  current  flow- 
ing in  the  coils  to  the  right  of  line  E  passes  to  segment  6,  and 
thus  reaches  the  brush,  while  the  current  flowing  in  the  coils 
to  the  left  of  line  E  reaches  segment  a,  and  through  this  passes 
to  the  brush.  As  the  brush  rests  upon  segments  a  and  b  the 
coil  with  which  they  connect  is  short-circuited,  and  therefore  a 


HANDBOOK    ON    ENGINEERING. 


85 


current  can  flow  in  it  in  any  direction,  or  there  may  be  no  cur- 
rent. To  be  able  to  run  without  spark,  or  to  obtain  perfect 
commutation,  as  it  is  called,  the  current  in  this  short-circuited 
coil,  when  in  the  position  shown,  should  be  zero,  or  nearly  so. 
This  coil,  which  is  short-circuited  by  the  brush,  is  called  the  corn- 
mutated  coil,  or  the  coil  undergoing  commutation.  It  will  be 
noticed  that  this  commutated  coiMs  in  a  position  just  forward  of 


Fig.  1. 

the  line  E ;  hence,  the  action  of  pole  P  will  be  to  develop  a 
current  in  it  that  will  flow  in  the  same  direction  as  the  current 
in  the  coils  ahead  of  it,  that  is,  in  the  coils  to  the  left.  Now  if 
this  current  flowed  through  the  brush,  it  would  be  in  a  direction 
contrary  to  that  of  the  arrow  at  a;  hence  it  would  act  to  check 
the  current  flowing  from  the  front  segment  a  to  the  brush,  and 
would  divert  it  through  the  commutated  coil  to  the  rear  segment 


86  HANDBOOK    ON    ENGINEERING. 

b.  If  the  action  of  pole  P  upon  the  eoramutated  coil  is  sufficiently 
vigorous,  the  current  developed  in  it  will  be  as  strong  as  the  cur- 
rent in  the  coils  ahead  of  it,  by  the  time  the  end  of  the  segment 
is  about  to  break  away  from  the  brush  ;  and  this  being  the  case 
there  will  be  no  current  from  segment  a  to  the  brush,  and  conse- 
quently, no  spark.  If  the  action  of  pole  P  is  not  strong  enough, 
then  there  will  be  a  small  current  from  segment  a  to  the  brush 
when  they  separate,  and  as  a  result,  a  small  spark.  If  the  action 
of  pole  P  on  the  commutated  coil  is  too  vigorous,  then  the  current 
developed  in  it  will  be  too  great,  and  it  will  not  only  divert  all 
the  current  coining  from 'the  forward  coils,  through  the  commuta- 
ted coil  to  segment  6,  but  in  addition  will  develop  a  local  current 
that  will  circulate  through  the  end  of  the  brush,  and,  therefore, 
when  the  separation  occurs,  there  will  be  a  current  flowing  from 
the  brush  to  the  front  segment,  and  consequently  a  spark. 

If  the  commutated  coil  were  placed  astride  of  line  E,  the 
action  of  pole  P  upon  it  would  be  no  greater  than  that  of  pole  JV,  so 
that  no  current  would  be  developed  in  it  while  undergoing  com- 
mutation. The  further  the  coil  is  in  advance  of  line  E,  when  short- 
circuited  by  the  brush,  the  stronger  the  action  of  pole  P  upon  it ; 
therefore,  the  strength  of  the  current  developed  in  the  commutated 
coil  can  be  increased  by  moving  the  brush  further  away  from  pole  P. 
Hence,  by  trial,  a  point  can  be  found  where  the  current  developed 
will  be  just  sufficient  for  the  purpose  and  no  more.  This  is  true, 
supposing  the  current  developed  by  the  armature  to  remain  con- 
stant, but,  if  it  varies,  the  current  in  the  commutated  coil  will  be 
either  too  great  or  too  small.  If,  when  the  brushes  are  set,  the 
armature  is  delivering  a  current  of,  say,  twenty  amperes,  then  the 
current  flowing  through  the  coils  to  the  left  of  the  brush  will  be 
ten  amperes,  and  the  current  in  the  commutated  coil  will  also  be 
ten  amperes.  If  the  armature  current  increases  to  forty  amperes, 
the  current  in  the  forward  coils  will  be  twenty  amperes,  and  as  that 
jn  the  commutated  coils  will  still  be  ten  amperes,  it  will  have  only 


HANDBOOK    ON    ENGINEERING.  87 

one-half  the  strength  required  for  perfect  commutation.  In  prac- 
tice, however,  it  is  found  that  if  the  commutator  have  a  sufficient 
number  of  segments,  and  the  proportions  of  the  machine  are  such 
that  the  line  E  remains  practically  in  the  same  position  for  all 
strengths  of  armature  current,  then,  if  the  brushes  are  set  so  as  to 
run  sparkless  with  an  average  load,  they  will  run  so  nearly  spark- 
less  with  a  heavy  or  light  load  as  to  make  it  difficult  to  detect  the 
difference. 

Even  when  a  machine  is  properly  proportioned,  the  brushes 
may  spark  badly  if  they  are  not  set  in  the  proper  position  and 
with  the  proper  tension.  If  the  tension  is  not  right,  they  will 
spark  no  matter  where  they  are  set.  If  the  tension  is  too  light, 
they  will  spark,  because  they  will  chatter  and  thus  jump  off  the 
surface  of  the  commutator.  If  the  tension  is  too  great,  they  will 
spark  because  they  will  cut  the  commutator,  and  then  the  latter 
will  act  as  a  file  or  grindstone  and  cut  away  particles  from  the 
brushes,  and  these  will  conduct  the  current  from  segment  to  seg- 
ment, as  well  as  from  the  segment  to  the  brush.  Whenever  a  com- 
mutator is  seen  to  be  covered  with  fine  sparks,  some  of  which  run 
all  the  way  around  the  circle,  it  may  be  depended  upon  that  the 
surface  is  rough,  due  in  most  cases  to  too  much  pressure  on  the 
brushes,  and  the  remedy  is  to  smooth  it  up  and  reduce  the  tension 
and  set  the  brushes  where  they  will  run  with  the  smallest  spark. 
When  the  brushes  begin  to  spark  they  rarely  cure  themselves  and 
the  longer  they  are  allowed  to  run  with  a  heavy  spark  the  worse 
they  will  get. 

Of  all  the  troubles  which  may  occur,  sparking  is  the  only  one 
which  is  very  different  in  the  different  types  of  machines.  In 
some  its  occurrence  is  practically  impossible.  In  others,  it  may 
result  from  a  number  of  causes.  The  following  cases  of  sparking 
apply  to  nearly  all  machines,  and  they  cover  closed-coil  dynamos 
and  motors  completely. 

Cause  J.  —  Brushes  not  set  at  the  neutral  point. 


88  HANDBOOK    ON    ENGINEERING. 

Symptom*  —  Sparking,  varied  by  shifting  the  brushes  with 
rocker-arm. 

Remedy* —  Carefully  shift  brushes  backwards  or  forwards 
until  sparking  is  reduced  to  a  minimum. 

The  usual  position  for  brushes  in  two-pole  mrchines  is 
opposite  the  spaces  between  the  pole-pieces. 

Cause  2*  —  Commutator  rough,  eccentric,  or  has  one  or  more 
"  high  bars  "  projecting  beyond  the  others,  or  one  or  more  flat 
bars,  commonly  called  "  flats,"  or  projecting  mica,  any  one  of 
which  causes  brush  to  vibrate,  or  to  be  actually  thrown  out  of 
contact  with  commutator. 

Symptom*  —  Note  whether  there  is  a  glaze  or  polish  on  the 
commutator,  which  shows  smooth  working  ;  touch  revolving  com- 
mutator with  tip  of  finger-nail,  and  the  least  roughness  is 
perceptible,  or  feel  of  brushes  to  see  if  there  is  any  jar.  If  the 
machine  runs  at  high-voltage  (over  250),  the  commutator  or 
brushes  should  be  touched  with  a  small  stick  or  quill  to  avoid 
danger  of  shock.  In  the  case  of  an  eccentric  commutator,  careful 
examination  shows  a  rise  and  fall  of  the  brush  when  commutator 
turns  slowly,  or  a  chattering  of  brush  when  running  fast. 

Remedy*  —  Smooth  the  commutator  with  a  fine  file  or  fine  sand- 
paper, which  should  be  applied  by  a  block  of  wood  which  exactly 
fits  the  commutator  (in  latter  case,  be  careful  to  remove  any  sand 
remaining  afterward  ;  and  never  use  emery) .  If  bearing  is  loose 
put  in  new  one.  If  commutator  is  very  rough  or  eccentric,  it 
should  be  taken  out  and  turned  off. 

Cause  3*  —  Brushes  make  poor  contact  with  commutator, 

Symptom*  —  Close  examination  shows  that  brushes  touch  only 
at  one  corner,  or  only  in  front  or  behind,  or  there  is  dirt  on  sur- 
face of  contact.  Sometimes,  owing  to  the  presence  of  too  much 
oil  or  from  other  cause,  the  brushes  and  commutator  become  very 
dirty  and  covered  with  smut.  They  should  then  be  carefully 
cleaned  by  wiping  with  oily  rag  or  benzine,  or  by  other  means. 


HANDBOOK    ON    ENGINEERING.  89 

Occasionally  a  "  glass-hard  "  carbon  brush  is  met  with.  It 
is  incapable  of  wearing  to  a  good  seat  or  contact  and  will  only 
touch  in  one  or  two  points,  and  should  be  discarded. 

Remedy*  —  File,  bend,  adjust  or  clean  brushes  until  they  rest 
evenly  on  commutator,  with  considerable  surface  of  contact  and 
with  sure  but  light  pressure. 

It  sometimes  happens  that  the  brushes  make  poor  contact, 
because  the  brush-holders  do  not  turn  or  work  freely. 

Cause  4. —  Short-circuited  coil  in  armature  or  reversed  coil. 

Symptom.  —  A  motor  will  draw  excessive  current,  even  when 
running  free  without  load.  A  dynamo  will  require  considerable 
power  even  without  any  load. 

The  short-circuited  coil  is  heated  much  more  than  the  others, 
and  is  very  apt  to  be  burnt  out  entirely  ;  therefore,  stop  machine 
immediately.  If  necessary  to  run  machine  to  locate  the  short- 
circuit,  one  or  two  minutes  is  long  enough,  but  it  may  be  re- 
peated until  the  short-circuited  coil  is  found  by  feeling  the  arma- 
ture all  over. 

An  iron  screw-driver  or  other  tool  held  between  the  field- 
magnets  near  the  revolving  armature  vibrates  very  perceptibly 
as  the  short-circuited  coil  passes.  Almost  any  armature,  par- 
ticularly one  with  teeth,  will  cause  a  slight  but  rapid  vibration  of 
a  piece  of  iron  held  near  it,  but  a  short-circuit  produces  a 
much  stronger  effect  only  once  per  revolution. 

The  current  pulsates  and  torque  is  unequal  at  different  parts 
of  a  revolution,  these  being  particularly  noticeable  when  arma- 
ture turns  rather  slowly.  If  a  large  portion  of  the  armature  is 
short-circuited,  the  heating  is  distributed  and  harder  to  locate. 
In  this  case  a  motor  runs  very  slowly,  giving  little  power,  but 
having  full-field  magnetism. 

Remedy.  —  A  short  circuit  is  often  caused  by  a  piece  of  solder 
or  other  metal  getting  between  the  commutator  bars  or  their  con- 
nections with  the  armature,  and  sometimes  the  insulation  between 


90  HANDBOOK    ON    ENGINEERING. 

or  at  the  ends  of  these  bars  is  bridged  over  by  a  particle  of  metal. 
In  any  such  case  the  trouble  is  easily  found  and  corrected.  If, 
however,  the  short-circuit  is  in  the  coil  itself,  the  only  real  cure  is 
to  rewind  the  coil. 

One  or  more  "  grounds  "  in  the  armature  may  produce  effects 
similar  to  those  arising  from  a  short  circuit. 

Cause  5. —  Broken  circuit  in  armature. 

Symptom*  —  Commutator  flashes  violently  while  running,  and 
commutator-bar  nearest  the  break  is  badly  cut  and  burnt ;  but  in 
this  case  110  particular  armature  coil  will  be  heated,  as  in  the  last 
case  and  the  flashing  will  be  very  much  worse,  even  when  turn- 
ing slowly.  This  trouble,  which  might  also  be  confounded 
with  a  bad  case  of  "  high-bar  "  or  eccentricity  in  commutator 
(sparking),  is  distinguished  from  it  by  slowly  turning  the  arma- 
ture, when  violent  flashing  will  continue  if  circuit  is  broken, 
but  not  with  eccentric  commutator  or  even  with  "  high  bar." 

Remedy*  —  The  trouble  is  often  found  where  the  armature 
wires  connect  with  the  commutator  and  not  in  the  coil  itself,  and 
the  break  may  be  repaired  or  the  loose  wire  may  be  resoldered  or 
screwed  back  in  place.  If  the  trouble  is  due  to  a  broken  com- 
mutator connection  and  it  cannot  be  fixed,  then  connect  the  dis- 
connected bar  to  the  next  by  solder,  or  "  stagger  "  the  brushes  ; 
that  is,  put  one  a  little  forward  and  the  other  back  so  as  to  bridge 
over  the  break.  If  the  break  is  in  the  coil  itself,  rewinding  is 
generally  the  only  cure. 

Cause  6*  —  Weak  field-magnetism. 

Symptom* — Any  considerable  vibration  is  almost  sure  to  pro- 
duce sparking,  of  which  it  is  a  common  cause.  This  sparking 
may  be  reduced  by  increasing  the  pressure  of  the  brushes  on  the 
commutator,  but  the  vibration  itself  should  be  overcome  by  the 
remedies  referred  to  above. 

Cause  7*  —  Chatter  of  Brushes.     The  commutator  sometimes 


HANDBOOK    ON    ENGINEERING.  91 

becomes  sticky  when  carbon  brushes  are  used,  causing  friction, 
which  throws  the  brushes  into  rapid  vibration  as  the  commutator 
revolves,  similarly  to  the  action  of  a  violin-bow. 

Symptom.  —  Slight  tingling  or  jarring  is  felt  in  brushes. 

Remedy*  — Clean  commutator  and  oil  slightly.  This  stops  it 
at  once. 

NOISE. 

Cause  8.  —  Vibration  due  to  armature  or  pulley  being  out  of 
balance'. 

Symptom*  —  Strong  vibration  felt  when  the  hand  is  placed 
upon  the  machine  while  it  is  running.  Vibration  changes  greatly 
if  speed  is  changed. 

Remedy* — The  easiest  method  of  finding  in  which  direction 
the  armature  is  out  of  balance  is  to  take  it  out  and  rest  the  shaft 
on  two  parallel  and  horizontal  A-shaped  metallic  tracks  suffici- 
ently far  apart  to  allow  the  armature  to  go  between  them.  If  the 
armature  is  then  slowly  rolled  back  and  forth,  the  heavy  side  will 
tend  to  turn  downward.  The  armature  and  pulley  should  always 
be  balanced  separately.  An  excess  of  weight  on  one  side  of  the 
pulley  and  an  equal  excess  of  weight  on  the  opposite  side  of  the 
armature  will  not  produce  a  balance  while  running,  though  it 
does  when  standing  still ;  on  the  contrary,  it  will  give  the  shaft 
a  strong  tendency  to  "wobble."  A  perfect  balance  is  only 
obtained  when  the  weights  are  directly  opposite,  i.  e.,  in  the 
same  line  perpendicular  to  the  shaft. 

Cause  9*  —  Armature  strikes  or  rubs  against  pole  pieces. 

Symptom. — Easily  detected  by  placing  the  ear  near  the  pole- 
pieces,  or  by  examining  armature  to  see  if  its  surface  is  abraded 
at  any  point,  or  by  examining  each  part  of  the  space  between 
armature  and  field,  as  armature  is  slowly  revolved,  to  see  if  any 


92  HANDBOOK    ON    ENGINEERING. 

portion  of  it  touches  or  is  so  close  as  to  be  likely  to  touch  when 
the  machine  is  running.  Or  turn  armature  by  hand  when  no 
current  is  on,  and  note  if  it  sticks  at  any  point. 

Remedy.  —  Bind  down  any  wire,  or  other  part  of  the  armature 
that  may  project  abnormally,  or  file  out  the  pole-pieces  where  the 
armature  strikes,  or  center  the  armature  so  that  there  is  a  uni~ 
form  clearance  between  it  and  the  pole-pieces  at  all  points. 

Cause  tO*  —  Singing  or  hissing  of  brushes.  This  is  usually 
occasioned  by  rough  or  sticky  commutator,  or  by  tips  of  brushes 
not  being  smooth,  or  the  layers  of  a  copper  brush  not  being  held 
together  and  in  place.  With  carbon  brushes,  hissing  will  be  caused 
by  the  use  of  carbon  which  is  gritty  or  too  hard.  Vertical  carbon 
brushes,  or  brushes  inclined  against  the  direction  of  rotation,  are 
apt  to  squeak  or  sing.  A  new  machine  will  sometimes  make 
noise  from  rough  commutator,  no  matter  how  carefully  it  is 
turned  off,  because  the  difference  in  hardness  between  mica  and 
copper  causes  the  cut  .of  the  tool  to  vary,  thus  forming  inequali- 
ties which  are  very  minute,  but  enough  to  make  noise.  This 
can  be  best  smoothed  by  running. 

Remedy* — Apply  a  very  little  oil  or  vaseline  to  the  com- 
mutator with  the  finger  or  a  rag.  Adjust  the  brushes  or  smooth 
the  commutator.  Carbon  brushes  are  apt  to  squeak  in  starting 
up,  or  at  slow  speed.  This  decreases  at  full  speed,  and  can 
usually  be  reduced  by  moistening  the  brush  with  oil,  care  being 
taken  not  to  have  a  ay  drops,  or  excess  of  oil.  Shortening  or 
lengthening  the  brushes  sometimes  stops  the  noise.  Run  the 
machine  on  open  circuit  until  commutator  and  brushes  are 
worn  smooth. 


HANDBOOK    ON    ENGINEERING.  93 


HEATING  IN  DYNAHO  OR  MOTOR. 

General  Instructions*  — The  degree  of  heat  that  is  injurious  or 
objectionable  in  any  part  of  a  dynamo  or  motor  is  easily  deter- 
mined by  feeling  the  various  parts.  If  the  heat  is  bearable  for  a 
few  moments,  it  is  entirely  harmless.  But  if  the  heat  is  unbear- 
able for  more  than  a  few  seconds,  the  safe  limit  of  temperature 
has  been  passed,  except  in  the  case  of  commutators  in  which 
solder  is  not  used  ;  and  it  should  be  reduced  in  some  of  the  ways 
that  are  given  above.  In  testing  with  the  hand,  allowance  should 
always  be  made  for  the  fact  that  bare  metal  feels  much  hotter 
than  cotton,  etc.  If  the  heat  has  become  so  great  as  to  produce 
an  odor  or  smoke,  the  safe  limit  has  been  far  exceeded  and  the 
current  should  be  shut  off  and  the  machine  stopped  immediately, 
as  this  indicates  a  serious  trouble,  such  as  a  short-circuited  coil  or 
a  tight  bearing.  The  machine  should  not  again  be  started  until 
the  cause  of  the  trouble  has  been  found  and  positively  overcome. 

Of  course  neither  water  nor  ice  should  ever  be  used  to  cool  elec- 
« 

trical  machinery,  except  possibly  the  bearings  of  large  machines, 
where  it  can  be  applied  without  danger  of  wetting  the  other 
parts. 

Feeling1  for  heat  will  answer  in  ordina^  cases,  but  of  course, 
the  sensitiveness  of  the  hand  differs,  and  it  makes  a  very  great 
difference  whether  the  surface  is  a  good  or  bad  conductor  of  heat. 
The  back  of  the  hand  is  more  sensitive  and  less  variable  than  the 
palm  for  this  test.  But  for  accurate  results  a  thermometer 
should  be  applied  and  covered  with  waste  or  cloth -to  keep  in 
the  heat.  In  proper  working  the  temperature  of  no  parts  of 
the  machine  should  rise  more  than  45°  C.,  or  81°  F.  above  the  tem- 
perature of  the  surrounding  air.  If  the  actual  temperature  of 


94  HANDBOOK    ON    ENGINEERING. 

the  machine  is  near  the  boiling  point,  100°  C.,  or  212°  F.,  it  is 
seriously  high. 

It  is  very  important  in  all  cases  of  heating  to  locate  correctly 
the  source  of  heat  in  the  exact  part  in  which  it  is  produced.  It 
is  a  common  mistake  to  suppose  that  any  part  of  a  machine  which 
is  found  to  be  hot  is  the  seat  of  the  trouble.  A  hot  bearing  may 
cause  the  armature  or  commutator  to  heat  or  vice  versa.  In 
every  case,  all  parts  of  the  machine  should  be  felt  to  find  which 
is  the  hottest,  since  heat  generated  in  one  part  is  rapidly  diffused 
throughout  the  entire  machine.  It  is  generally  much  surer  and 
easier  in  the  end  to  make  observations  for  heating  by  starting 
with  the  whole  machine  perfectly  cool,  which  is  done  by  letting  it 
stand  for  one  or  more  hours  or  over  night,  before  making  the 
examination.  When  ready  to  try  it,  run  it  fast  for  three  to  five 
minutes,  with  the  field  magnets  charged ;  then  stop,  and  feel  all 
parts  immediately.  The  heat  will  be  found  in  the  right  place,  as 
it  will  not  have  had  time  to  diffuse  from  the  heated  to  the  cool 
parts  of  the  machine.  Whereas,  after  the  machine  has  run  some 
time,  any  heating  effect  will  spread  until  all  parts  are  equal  in 
temperature,  and  it  will  then  be  almost  impossible  to  locate  the 
trouble. 

Excessive  heating  of  commutator,  armature,  field  magnets,  or 
bearings  may  occur  in  any  type  of  dynamo  or  motor,  but  it  can 
almost  always  be  avoided  by  proper  care  and  working  conditions. 


THE  EFFECT  OF  THE   DISPLACEHENT  OF  THE  ARMATURE. 

If  a  machine  is  old,  it  is  more  than  likely  the  shaft  will  be 
found  out  of  center,  and  if  this  fact  is  discovered  at  a  time  when 
things  are  not  working  as  they  should,  it  is  taken  for  granted  this 
is  the  cause  of  the  trouble.  What  is  true  of  shafts  out  of  the 


HANDBOOK    ON   ENGINEERING. 


95 


center  is  true  of  several  other  things  that  are  liable  to  get  out  of 
place.  For  the  present  it  will  be  sufficient  to  investigate  just 
what  effect  the  displacement  of  the  shaft  can  have. 

Fig.  \  illustrates  an  armature  of  a  two-pole  machine  which  is 
out  of  center  in  one  direction,  and  Fig.  2  shows  another  two-pole 
armature  out  of  center  in  a  direction  of  right  angles  to  that 
shown  in  the  first  figure.  The  condition  shown  in  Fig.  1  could 
be  produced  by  a  heavy  armature  running  in  rather  light  bear- 
ings for  several  years,  and  the  side  displacement  of  Fig.  2  could 
be  produced  by  the  tension  of  an  extra  tight  belt.  The  mechan- 


Fig.  1. 


Fig.  2. 


ical  effect  of  both  these  conditions  would  be  to  increase  the  pres- 
sure on  the  bearings,  as  the  part  a  of  the  armature  would  be 
drawn  toward  the  poles  of  the  field  with  greater  force  than  the 
opposite  side.  The  downward  pull,  due  to  the  attraction  of  the 
magnetism,  would  be  greater  in  Fig.  1  than  the  side  pull  in  Fig. 
2,  supposing  both  armatures  and  fields  to  be  the  same  in  both 
cases,  and  the  displacement  of  the  shafts  equal.  This  difference 
is  due  to  the  fact  that  in  Fig.  1  the  magnetism  of  both  poles  is 
concentrated  at  the  lower  corners  on  account  of  the  shorter  air 
gap ;  hence  both  sides  pull  much  harder  on  the  lower  side.  In 


96  HANDBOOK   ON   ENGINEERING. 

Fig.  2  the  pull  of  the  N  pole  is  greater  than  that  of  the  other, 
simply  because  in  the  latter  the  magnetism  ia  more  dispersed,  but 
the  difference  in  the  density  on  the  two  sides  will  not  be  very 
great.  If  the  bearings  of  a  machine,  with  the  armature  dis- 
placed, as  indicated,  have  shown  any  signs  of  cutting,  or  if  they 
run  unusually  warm,  their  condition  will  be  improved  by  putting 
in  new  bearings  that  will  bring  the  shaft  central. 

If  the  armature  is  of  the  drum  type,  the  displacement  of  the 
shaft  will  have  no  effect  upon  it  electrically.  This  is  owing  to  the 
fact  that  all  the  armature  coils  are  wound  from  one  side  of 
the  core  to  the  other,  and,  therefore,  at  all  times,  every 
coil  has  one  side  under  the  influence  of  one  pole  and  the  other 
side  under  the  influence  of  the  opposite  pole,  and  if  one 
side  is  acted  upon  strongly  by  one  pole,  it  will  be  acted 
upon  feebly  by  the  other.  If  the  armature  is  of  the  ring  type, 
then  the  displacement  of  the  shaft  will  affect  it  electrically,  for 
in  a  ring  armature,  the  coils  on  one  side  are  acted  upon  by 
the  pole  on  that  side,  only,  and  as  the  magnetic  field  from  one 
pqlewill  be  stronger  than  that  from  the  other  (that  is,  considering 
the  action  upon  equal  halves  of  the  armature) ,  the  voltage  devel- 
oped in  the  coils  on  one  side  of  the  armature  will  be  greater  than 
that  developed  on  the  other  side. 

The  effect  of  the  disturbance  of  the  electrical  balance  will  be 
that  the  brushes  will  spark  badly,  because  the  voltage  of  the  cur- 
rent generated  on  one  side  of  the  armature  will  be  greater  than 
that  of  the  current  on  the  other  side.  Hence,  when  these  two 
currents  meet  at  the  brushes,  the  strong  one  will  tend  to  drive 
the  weak  one  backward.  If,  while  the  armature  is  out  of  center, 
we  wish  to  adjust  the  brushes  so  as  to  get  rid  of  the  excessive 
sparking,  all  we  have  to  do  is  to  set  them  to  the  right  of  the  cen- 
ter line,  as  in  Fig.  2,  so  that  the  wire  on  the  left  side  will  cover  a 
greater  portion  of  the  circumference  than  the  right. 


HANDBOOK   ON   ENGINEERING.  97 

In  a  multipolar  machine,  the  displacement  of  the  armature 
will  have  the  same  effect  mechanically  as  in  the  two-pole  type ; 
multipolar  armatures  are  connected  in  two  different  ways,  one  of 
which  is  called  the  wave  or  series  winding,  and  the  other  the  lap 
or  parallel  winding.  In  the  first  named  type  of  winding,  the 
ends  of  all  the  coils  on  the  armature  are  connected  with  each 
other  and  with  the  commutator  segments  in  such. a  manner  that 
there  are  only  two  paths  through  the  wire  for  the  current ;  there- 
fore, these  two  armature  currents  pass  under  all  the  poles  and 
the  voltage  of  each  current  is  the  combined  effect  of  all  the  poles. 
From  this  very  fact,  it  can  be  clearly  seen  that  it  makes  no 
difference  what  the  distance  between  the  several  poles  and  arma- 
ture may  be,  for  if  some  are  nearer  than  the  others,  the  only 
effect  will  be  that  these  poles  will  not  develop  their  share  of  the 
total  voltage,  but  whatever  their  action  may  be,  it  will  be  the 
same  on  the  coils  in  both  circuits. 

When  a  multipolar  armature  is  connected  so  as  to  form  a 
parallel  or  lap  winding,  then  the  connections  between  the  coil 
ends,  and  between  these  ends  and  the  commutator  segments,  are 
such  that  as  many  paths  are  provided  for  the  current  as  there  are 
poles,  and  each  one  of  these  paths  is  located  under  one  pole,  and 
as  a  consequence,  the  voltage  developed  in  it  is  proportional  to 
the  action  of  this  pole.  The  diagram  3  illustrates  a  six-pole 
armature  with  the  ends  of  the  field  poles,  and  the  arrows  a  a,  b  6, 
c  c,  indicate  the  six  separate  divisions  of  the  coils  in  which  the 
branch  currents  are  developed.  Now,  it  can  be  clearly  seen  that 
as  the  armature  is  nearer  to  the  lower  poles  than  to  any  of  the 
others,  the  action  of  these  will  be  the  strongest.  Hence,  the  cur- 
rents a  a  will  be  stronger  than  the  others  and  will  have  a  higher 
voltage. 

The  two  upper  currents  are  weaker  than  the  side  ones  and 

7 


98 


HANDBOOK    ON    ENGINEERING. 


their  voltage  is  also  lower,  so  that,  the  current  returning  to  the 
commutator  through  the  brushes  at  the  upper  corners,  will  not 
divide  equally,  but  the  larger  portion  will  be  drawn  into  the  coils 
on  the  side ;  and  as  the  upper  coils  will  have  to  fight  to  hold  their 
own,  so  to  speak,  there  will  be  a  disturbance  of  the  balance  that 


Fig.  3. 


is  required  for  smooth  running.  The  result  will  be  heavy  spark- 
ing at  these  brushes.  In  the.great  majority  of  cases,  if  the  brushes 
of  a  multipolar  machine  spark  on  account  of  tffe  armature  being 
out  of  center,  the  only  cure  is  to  reset  the  bearings,  if  they  are 
adjustable,  and  if  they  are  not,  to  put  in  new  ones. 


HANDBOOK    ON    ENGINEERING.  101 

Soldering1   Fluid* — «.  The    following   formula   for    soldering 
fluid  is  suggested  :  — 

Saturated  solution  of  zinc  chloride,  5  parts. 
Alcohol,  4  parts. 

Glycerine,  1  part. 

Bell  or  Other  Wires*  —  a.  Shall   never  be  run  in  same  duct 
with  lighting  or  power  wires. 

Table  of  Capacity  of  Wires*  — 


1 

73 
fl 

IN 

w 

p 

OQ 

1* 

1 
OQ 

H 
o> 
A 

cSO 

* 

"0°^ 

9 

^ii 

£ 

CQ 

K 

<< 

6 

N 

^ 

35 

19 

1,288 

... 

... 

... 

18 

1,624 

... 

... 

3 

17 

2,048 

... 

... 

... 

16  . 

2,583 

... 

... 

6 

15 

3,257 

... 

... 

... 

14 

4,107 

... 

... 

12 

12 

6,530 

... 

17 

... 

9,016 

7 

19 

21 

... 

11,368 

7 

18 

25 

... 

14,336 

7 

17 

30 

... 

18,081 

7 

16 

35 

... 

22,799 

7 

15 

40 

... 

30,856 

19 

18 

50 

... 

38,912 

19 

17 

60 

... 

49,077 

19 

16 

70 

... 

60,088 

37 

18 

85 

... 

75,776 

37 

17 

100 

... 

99,064 

61 

18 

120 

.0. 

124,928 

61 

17 

145 

•  »• 

157,563 

61 

16 

170 

102 


HANDBOOK    ON     ENGINEERING . 


"3      K 

8« 


198,677  01  15  200 

250,527  61  14  235 

296,387  91  15  270 

373,737  91  14  320 

413,639  127  15  340 

When  greater  conducting  area  than  that  of  B.  &  S.  G.  is  re- 
quired, the  conductor  shall  be  stranded  in  a  series  of  7,  19,  37, 
61,  91  or  127  wires,  as  may  be  required ;  the  strand  consisting 
of  one  central  wire,  the  remainder  laid  around  it  concentrically, 
each  layer  to  be  twisted  in  the  opposite  direction  from  the  pre- 
ceding. / 

TABLE    SHOWING     THE    SIZE    OF    WIRE    OF     DIFFERENT    METALS    THAI- 
WILL    BE    MELTED    BY    CURRENTS    OF    VARIOUS    STRENGTHS. 


Strength 
of 
Current 
in 
Amperes. 

DIAMETER  OF  WIHE  IN  THOUSANDTHS  OF  AN  INCH. 

Copper. 

Aluminum. 

Platinum. 

German 
Silver. 

Iron. 

Tin. 

1 

.002 

.003 

.003 

.003 

.005 

.007 

2 

.003 

.004 

.005 

.005 

.008 

.011 

3 

.004 

.005 

.007 

.007 

.010 

.015 

4 

.005 

.006 

.008 

.008    . 

.012 

.018 

5 

.006 

.008 

.010 

.010 

.014 

.021 

10 

.009 

.012 

.016 

.016 

.022 

.033 

15 

.013 

.016 

.020 

.020 

.028 

.044 

20 

.015 

.019 

.025 

.025 

.034 

.053 

25 

.018 

.022 

.029 

.029 

.040 

.062 

30 

.020 

.025 

.032 

.032 

.045 

.069 

35 

.022 

.028 

.036 

.036 

.050 

.077 

40 

.025 

.030 

.039 

.039 

.055 

.084 

50 

.027 

.033 

.042 

.042 

.059 

.091 

60 

.029 

.035 

.045 

.045 

.063 

.098 

HANDBOOK    ON    ENGINEERING.  103 


CHAPTER     IX. 

INSTRUCTIONS    FOR    INSTALLING   AND  OPERATING  APPAR- 
ATUS FOR  ARC  LIGHTING,  BRUSH  SYSTEM. 

Theory  of  the  Brush  arc  generator.  —  The  Brush  Arc  Gen- 
erator is  of  the  open  coil  type,  the  fundamental  principle  of  which 
is  illustrated  in  Fig.  1.  Two  pairs  of  coils,  placed  at  right  angles 


Fig.   I. 

on  an  iron  core,  are  rotated  in  a  magnetic  field.  The  horizontal 
coils  represented  in  the  diagram  are  producing  their  maximum 
electromotive  force,  while  the  pair  of  coils  at  right  angles  to  them 
is  generating  practically  no  electromotive  force.  The  brushes 
are  placed  on  the  segments  of  the  four-part  commutator,  so  as  to 
collect  only  the  current  generated  by  the  two  horizontal  coils. 
The  other  coils  are  open  circuited,  or  completely  cut  out  of  the 
circuit. 


102 


HANDBOOK    ON     ENGINEERING. 


•H 

«g 

CO 

o 

<j 

6 

198,677 

61 

250,527 

61 

296,387 

91 

373,737 

91 

413,639 

127 

15 
14 
15 
14 
15 


200 
235 
270 
320 
340 


When  greater  conducting  area  than  that  of  B.  &  S.  G.  is  re- 
quired, the  conductor  shall  be  stranded  in  a  series  of  7,  19,  37, 
61,  91  or  127  wires,  as  may  be  required;  the  strand  consisting 
of  one  central  wire,  the  remainder  laid  around  it  concentrically, 
each  layer  to  be  twisted  in  the  opposite  direction  from  the  pre- 
ceding, t 

TABLE    SHOWING     THE    SIZE    OF    WIRE    OF     DIFFERENT    METALS    THAT 
WILL    BE    MELTED    BY    CURRENTS    OF    VARIOUS    STRENGTHS. 


Strength 
of 
Current 
in 
Amperes. 

DIAMETER  OF  WIHE  IN  THOUSANDTHS  OF  AN  INCH. 

Copper. 

Aluminum. 

Platinum. 

German 
Silver. 

Iron. 

Tin. 

1 

.002 

.003 

.003 

.003 

.005 

.007 

2 

.003 

.004 

.005 

.005 

.008 

.011 

3 

.004 

.005 

.007 

.007 

.010 

.015 

4 

.005 

.006 

.008 

.008    . 

.012 

.018 

5 

.006 

.008 

.010 

.010 

.014 

.021 

10 

.009 

.012 

.016 

.016 

.022 

.033 

15 

.013 

.016 

.020 

.020 

.028 

.044 

20 

.015 

.019 

.025 

.025 

.034 

.053 

25 

.018 

.022 

.029 

.029 

.040 

.062 

30 

.020 

.025 

.032 

.032 

.045 

.069 

35 

.022 

.028 

.036 

.036 

.050 

.077 

40 

.025 

.030 

.039 

.039 

.055 

.084 

50 

.027 

.033 

.042 

.042 

.059 

.091 

60 

.029 

.035 

.045 

.045 

.063 

.098 

HANDBOOK    ON    ENGINEERING.  103 


CHAPTER     IX. 

INSTRUCTIONS    FOR    INSTALLING   AND  OPERATING  APPAR- 
ATUS FOR  ARC  LIGHTING,  BRUSH  SYSTEM. 

Theory  of  the  Brush  arc  generator.  —  The  Brush  Arc  Gen- 
erator is  of  the  open  coil  type,  the  fundamental  principle  of  which 
is  illustrated  in  Fig.  1.  Two  pairs  of  coils,  placed  at  right  angles 

\ 


Fig.   i. 

on  an  iron  core,  are  rotated  in  a  magnetic  field.  The  horizontal 
coils  represented  in  the  diagram  are  producing  their  maximum 
electromotive  force,  while  the  pair  of  coils  at  right  angles  to  them 
is  generating  practically  no  electromotive  force.  The  brushes 
are  placed  on  the  segments  of  the  four-part  commutator,  so  as  to 
collect  only  the  current  generated  by  the  two  horizontal  coils. 
The  other  coils  are  open  circuited,  or  completely  cut  out  of  the 
circuit. 


104  HANDBOOK  ON  ENGINEERING. 

Such  a  machine  will  generate  current,  continuous  in  direction, 
but  fluctuating  considerably  in  amount.  These  fluctuations  will 
be  diminished  by  the  addition  of  more  coils  to  the  armature. 


Fig*  2  is  a  diagrammatic  representation  of  an  eight  coil 
machine.  The  ends  of  coils  diametrically  opposite  are  connected 
as  in  the  four-pole  machine,  but  to  avoid  complications,  these 
connections  have  been  omitted  on  the  diagram.  In  the  eight  coil 
machine,  one  pair  of  coils,  A1,  A2,  is  generating  maximum  elec- 
tromotive force.  At  right  angles  to  these  coils,  the  coils  Cl  and 
O2  are  generating  no  electromotive  force.  In  intermediate 
positions,  the  coils  jB1,  JB2,  D1,  D2  are  generating  a  useful  electro- 
motive force,  although  one  which  is  not  so  high  as  that  generated 
by  the  coils  A1  and  A2. 

In  collecting  the  current  from  such  an  armature,  the  coils  in 
the  intermediate  positions  cannot  be  connected  in  parallel  with 
the  coils  generating  maximum  electromotive  force,  because  their 
electromotive  force  is  lower.  The  pair  of  coils  A1,  A*  can,  how- 
ever, be  placed  in  series  and  connected  in  series  with  the  two  pairs 


HANDBOOK   ON   ENGINEERING. 


105 


of  coils  .B1,  .B2  and  Z)1,  Z)2,  which  may  be  placed  in  parallel  with 
each  other,  since  they  occupy  similar  positions  in  the  magnetic  fiedl. 

In  the  Brush  Arc  Generator  a  double  commutator  is  used  to 
automatically  make  these  connections. 

In  Fig.  3  this  commutator  is  developed  or  spread  out,  and  the 
coils  are  represented  diagrammatically. 


Fig.  3- 


BIPOLAR  BRUSH  ARC  GENERATORS. 

Bipolar  Brush  Machines  were  built  in  eight  sizes,  ranging 
in  capacity  from  1  to  65  lamps  of  2000  candle-power,  and  2  to 

45  lamps  of  1200  candle- 
power. 

Although  now  su- 
perseded by  the  larger 
multipolar  machines,  so 
many  bipolar  machines 
are  still  in  use  that  I 
consider  it  advisable  to 
publish  the  following  in- 


J06  HANDBOOK   ON    ENGINEERING. 

structions  for  operating  and  making  such  repairs  as  become  nec- 
essary after  the  long  service  which  thousands  of  these  machines 
have  undergone. 

The  general  construction  of  the  bipolar  machine  is  shown  on 
page  105.  Four  field  spools  are  provided,  one  pair  to  each  side 
of  the  armature.  The  field  cores  are  bolted  to  vertical  yokes  at 
each  end  of  the  machine,  which  also  carry  the  bearings  for  the 
armature  shaft. 

The  machines  should  be  set  up  in  the  manner  described  under 
Multipolar  Generators.  To  operate  satisfactorily,  the  machines 
must  be  kept  perfectly  clean,  the  oil  cups  well  filled  and  the  com- 
mutator surfaces  smooth. 

The  armature  with  its  shaft  may  be  readily  removed  after 
unscrewing  the  bolts  and  lifting  the  caps  from  the  bearings  at 
each  end. 

Each  coil  or  bobbin  on  the  armature  is  wound  independently, 
and  may  be  rewound  without  disturbing  any  other  part  of  the 
armature.  The  inside  ends  of  coils  diametrically  opposite  are 
connected  together,  while  their  opposite  ends  are  connected  by 
means  of  wires  running  through  the  hollow  shaft  to  opposite 
segments  of  the  commutator.* 

Proper  connections  are  made  by  having  separate  brushes  for 
each  commutator  ring  consisting  of  two  pairs  of  segments.  Thus 
in  an  eight  coil  machine,  the  lower  brush  on  one  commutator  ring 
is  connected  to  the  upper  brush  on  the  next  ring. 

The  commutator  segments  are  mounted  on  an  insulated  body, 
and  when  worn  out  may  be  easily  replaced. 


*  That  is  for  2000  and  1200  candle-power  machines.  On  machines  for 
4000  candle-power,  each  pair  of  opposite  coils  is  connected  in  multiple 
instead  of  as  above  described. 


HANDBOOK    ON    ENGINEERING. 


107 


CONNECTIONS  OF  NO  j£  AND  NO.  8  BIPOLAR  GENERATORS. 

'  The  field  switch  on  the  No.  7J  and  No.  8  machines  is  dif- 
ferent from  that  of  the  smaller  sizes,  and  there  is  but  one  small 
binding  post  for  connection  to  the  regulator.  The  internal  con- 
nections of  the  regulator  are  also  slightly  different.  The  inside 


TT 


^\fLf,      Ammeter 

dOL 


Counter  Clockwise 


Fig.  4. 

terminal  of  one  upper  binding  post  K  (see  Fig.  4),  is  connected 
to  the  positive  (left-hand)  wire  which  connects  the  main  binding 
post  to  the  magnets  M. 

As  the  No*  7J  and  No.  8  machines  have  three  commutator 
rings,  cross-connections  between  the  brushes  are  required  as 
shown  in  the  diagram.  The  outside  left-hand  brush  is  connected 
across  to  the  middle  right-hand  brush,  and  the  middle  left-hand 
brush  is  connected  to  the  inside  right-hand  brush.  The  inside 
left-hand  brush  is  connected  to  the  fields,  and  to  the  shunt 
leading  to  the  regulator.  On  the  old  type  machines,  the  inside 
left-hand  brush  is  connected  to  the  right-hand  small  binding 
post. 


108 


HANDBOOK   ON   ENGINEERING. 


AUTOMATIC  REGULATOR   FOR  BIPOLAR  BRUSH  ARC  GENE- 
RATORS. 

The  Brush  Automatic  Regulator  or  "  Dial "  is  shown  in  the 
accompanying  illustration.  It  contains  a  variable  resistance  which 

is  connected  as  a  shunt  to  the 
fields,  and  automatically  changed 
to  increase  or  decrease  the  field 
current,  and  thus  the  voltage  of 
the  machine.  The  resistance  is 
composed  of  columns  of  carbon 
plates  which  rest  on  the  lever  L. 

When  the  current  rises  above 
normal,  the  magnets  M  draw  up 
the  lever  L  and  compress  the  car- 
bon columns,  reducing  their  resist- 
ance and  shunting  more  current 
from  the  fields.  The  electromo- 
tive force  of  the  generator  is  thus 
reduced  and  the  current  maintained 
constant.  As  the  resistance  of  the 
line  is  increased  by  the  addition  of 
lamps,  the  current  in  the  magnets 
M'  is  diminished  and  the  lever 
drops,  separating  the  carbons  and  increasing  the  resistance  of  the 
shunt.  More  of  the  current  must  then  pass  through  the  genera- 
tor fields  and  raise  the  electromotive  force  of  the  machine. 

The  dash  pot  P  is  to  prevent  sudden  changes  of  resistance, 
and  should  be  kept  full  of  pure  cylinder  oil  or  glycerine.  It 
should  move  easily,  so  that  the  regulator  can  respond  quickly  to 
changes  in  the  current. 


HANDBOOK   ON   ENGINEERING.  109 

The  variable  resistance  TF,  which  is  adjusted  by  the  spring  £, 
is  connected  as  a  shunt  to  the  magnet  coils  M  and  regulates  their 
current.  The  opening  of  the  contact  C  is  adjusted  by  the  fiber 
nut  N.  With  the  shunt  resistance  properly  adjusted  and  the 
lever  in  a  midway  position,  the  current  can  be  increased  by 
tightening  the  nut  N,  and  decreased  by  loosening  it.  When 
the  shunt  resistance  W  is  once  properly  adjusted,  it  should  not 
be  changed,  unless  the  magnets  M  are  changed. 

To  connect  the  regulator  into  the  circuit,  the  main  line  is 
brought  in  at  the  large  binding  posts  .B,  the  positive  being  con- 
nected to  the  left-hand  binding  post.  The  current  must  enter  at 
the  left  hand . 

The  small  binding  post  J  is  connected  with  the  small  binding 
post  on  the  generator,  so  that  the  carbon  resistance  plates  are  in 
shunt  with  the  field  of  the  generator. 

While  adjusting  the  regulator,  the  generator  should  run  at 
normal  speed,  and  the  first  test  should  be  made  on  short  circuit. 
If  the  current  is  too  low,  lever  L  should  begin  to  drop  at 
once  and  so  increase  the  current.  If  this  lever  should  stand  at 
its  lowest  position  and  the  current  still  remain  too  low  at  full 
load,  the  speed  of  the  generator  must  be  increased.  If  the  current 
is  too  high,  the  lever  should  rise  and  so  reduce  it ;  if  it  fails  to 
rise,  the  contact  G  should  be  examined.  The  current  at  this 
contact  should  spark  all  the  time.  If  the  lever  rises  when  the 
contact  is  below  normal  the  nut  N  should  be  tightened. 

The  resistance  of  the  shunt  W  should  be  so  adjusted  by 
removing  the  spring  8  that  the  lever  will  rise  when  the  contact  is 
opened  and  descend  when  the  contact  is  closed. 

.Once  in  six  months  the  carbon  resistance  columns  should  be 
loosened  up  and  the  dust  and  loose  carbon  particles  blown  out 
with  a  bellows.  The  regulator  must  then  be  readjusted. 


110 


HANDBOOK   ON    ENGINEERING. 


MULTIPOLAR  BRUSH  ARC  GENERATORS. 

Each  machine  is  provided  with  an  iron  bed-plate  fitted  with 
a  ratchet  and  screw  for  sliding  the  machine  to  adjust  the  belt 
tension.  This  bed-plate  should  be  securely  fastened  to  a  dry 
wood  sub-base  not  less  than  10"  in  thickness,  except  on  wood 
floors,  in  which  case  it  may  be  somewhat  less,  according  to  the 
thickness  of  the  floor. 


Multipolar  Brush  Arc  Generator. 

Unless  the  generator  can  be  set  up  on  a  substantial  floor  a 
foundation  of  masonry  must  be  built. 

In  whatever  manner  the  bed-plate  is  mounted,  the  greatest 
care  must  be  taken  to  have  a  thorough  and  permanent  insulation 
from  earth. 


HANDBOOK    ON    ENGINEERING. 


Ill 


Four  short  bolts  pass  through  the  generator  frame  and  are 
used  to  hold  the  machine  in  position  on  its  bed-plate.  They  are 
inserted  in  the  slots  in  the  iron  base-plate  and  provided  with 
square  nuts  at  their  lower  ends. 

The  lower  half  of  the  frame  is  first  placed  in  position  on  the 
bed-plate  and  bolted  down. 


Method  of  Suspending  Armature. 

The  lower  halves  of  the  bearing  boxes  should  be  removed 
and  the  oil  chambers  thoroughly  cleaned  and  filled  with  a  good 
quality  of  stringy  oil,  to  the  height  indicated  by  the  mark  on  the 
oil  gauge.  The  lower  halves  of  the  bearing  boxes  may  then  be 
replaced. 

The  proper  method  of    suspending  the  armature  is  shown  on 

page  111. 

When    handling  the    magnet  yokes,  a  rope  sling  should  be 


112 


HANDBOOK    ON   ENGINEERING. 


used,  as  shown  in  the  illustration  above.  The  bolts  should  be 
inserted  as  shown,  and  as  the  yoke  is  lowered,  these  will  act  as  a 
guide  and  drop  it  into  its  proper  place.  The  frame  bolts  must  be 


Method  of  Handling  the  Magnet  Yoke. 

screwed  up  especially  tight,  as  any  movement  of  the  yokes  while 
the  machinery  is  running  will  ruin  the  armature. 

The  brush-holder  yoke  and  the  regulator  rocker  arm  should 
be  put  in  place  with  a  little  oil  on  the  bearing  seats  to  insure  free- 
dom of  movement  through  the  entire  range. 

SETTING  THE  BRUSHES. 

A  pressure  brush  should  always  be  used  over  the  under  brush, 
as  it  improves  the  running  of  the  commutator  and  secures  a  bet- 


HANDBOOK    ON    ENGINEERING. 


113 


ter  contact  on  the  segment.     The  brushes  should  be  set  5J"  from 
the  front  side  of  the  brass  brush-holder. 

In  setting*  the  brushes,  commence  with  the  inner  pair  and  set 
one  brush  about  5J"  from  the  holder  to  the  tip  of  brush,  then 
rotate  the  rocker  or  armature  until  the  tip  of  the  brush  is  exactly 
in  line  with  the  end  of  a  copper  segment,  as  shown  in  Fig.  5. 
The  other  brush  should  be  set  on  the  corresponding  segment  90o 
removed,  but  if  the  length  of  the  brush  from  the  holder  is  less  than 
5 1",  move  both  brushes  forward  until  the  length  of  the  shorter 


brush  from  the  holder  is 
brushes  in  the  same  manner, 
clamping  firmly  in  position, 
and  by  using  a  straight  edge 
or  steel  rule,  all  the  brushes 
can  be  set  in  exactly  the 
same  line  and  firmly  se- 
cured. The  spark  on  one 
of  the  six  brushes  may 
be  a  trifle  longer  than  on 
the  others.-  In  this  case, 
move  the  brush 


Now. set  the  two  extreme  outer 


Fig.  6, 


Fig. 


Fig.  5. 
forward  a 

trifle  so  as  to  make  the  sparks  on  the  six 
brushes  about  the  same  length.  Equality  in 
the  spark  lengths  is  not  essential,  but  it  gives 
at  a  glance  an  indication  of  the  running  condi- 
tion of  the  machine. 

Brushes  should  not  bear  on  the  commutator 
as  illustrated  in  Fig.  6  ;  they  will  tend  to  drop 
into  the  commutator  slots  and  pound  the  copper 
tip  of  the  wood  block.  If  the  bearing  is  too  far 
from  the  end,  as  in  Fig.  7,  the  point  of  the  brush 
is  lifted  from  the  leaving  end  of  the  segment, 
causing  sparking. 


114  HANDBOOK    ON    ENGINEERING. 

Fig.  8  shows  correct  setting. 

CARE  OF  COMHUTATOR. 

I 

Fig.  8.  If  the  commutator  needs  lubrication,  oil  it 

very  sparingly.     Once  or  twice  during  a  run  is 

ample.     If  the   oil   has    a  tendency  to  blacken  the  commutator 

instead  of  making   it   bright,  wipe  the  commutator  with  a  dry 

cloth. 

The  machine,  of  course,  generates  high  potential,  and  the 
cloth,  or  whatever  is  used  to  oil  the  commutator,  should,  there- 
fore, be  placed  on  a  stick  so  that  the  hand  is  not  placed  in  any 
way  between  the  brushes. 

A  rubber  mat  should  be  provided  for  the  attendant  to  stand 
on  when  working  around  the  commutator  and  brushes. 

To  prevent  any  possibility  of  shock,  all  switches  on  the  termi- 
nal board  should  be- closed. 

As  soon  as  the  current  is  shut  off  from  the  machine,  the  com- 
mutator should  be  cleaned.  A  piece  of  very  fine  sandpaper  held 
against  the  commutator  under  a  strip  of  wood  for  about  a  minute 
before  the  machine  is  stopped,  will  scour  the  commutator  suffi- 
ciently. The  brushes  need  not  be  removed.  Never  use  a  file, 
emery  cloth,  or  crocus,  on  the  commutator.  New  blocks  will  some- 
times cause  flashing,  due  to  the  presence  of  sap  in  the  wood. 

CONNECTIONS  OF  HULTIPOLAR   BRUSH    ARC    GENERATORS. 

Connections  of  Multipolar  Brush  Arc  Generators  are  shown 
in  Diagram  No.  13442.  The  current  enters  the  field  from  the 
negative  side  of  the  circuit  and  takes  the  following  course :  Spool 
1,  to  2,  to  7,  to  8,  to  5,  to  6,  to  3,  to  4,  to  terminal  board,  to 
commutator.  The  field  current  is  in  the  same  direction  for  clock- 
wise and  counter  clockwise  machines. 


HANDBOOK    ON   ENGINEERING. 


115 


Diagram  No.    13442, 


116 


HANDBOOK   ON   ENGINEERING. 


The  current  of  the  Brush  Arc  Machine  is  automatically  main- 
tained constant  by  a  regulator  of  one  of  the  forms  described  on 
the  following  pages. 


FORM  i  REGULATOR  FOR   MULTIPOLAR  BRUSH  ARC  GENE- 

RATORS. 

The  Form  \  Regulator  is  placed  on  the  frame  of  the  machine 


, To  Controller 


ToControner 


Fig.  9, 


beneath  the  commutator,  and  a  constant  motion  is  imparted  to  its 
main   shaft  through  a  small  belt  running  around  the   armature 


HANDBOOK    ON    ENGINEERING.  117 

aaft.  (See  Fig.  9.)  By  means  of  magnetic  clutches  and 
evel  gears,  a  pinion  shaft  is  rotated,  which  moves  the  rack  and 
le  rocker  arm  and  so  shifts  the  brushes  on  the  commutator  ;  at 
ie  same  time  the  rheostat  arm  is  moved  over  the  contacts  to  cut 
jsistances  in  or  out  of  the  shunt  around  the  field  circuit. 

The  current  for  the  magnetic  clutches  is  regulated  by  the 
Dntroller. 

The  controller  consists  principally  of  two  magnets  which  are 
aergized  by  the  main  current  and  act  when  the  current  is  too 
igh  or  too  low,  by  sending  a  small  current  to  one  of  the  clutches. 

If  the  controller  is  out  of  adjustment  and  fails  to  keep  the  cur- 
snt  normal,  do  not  try  to  adjust  the  tensions  of  both  armatures 
;  the  same  time.  The  left-hand  spool  I  (see  Diagram  No. 
3454)  may  not  take  hold  quickly  enough,  or  the  spool  F  may 
tke  hold  too  quickly.  To  make  the  adjustment,  screw  up  the 
ij  listing  button  K  on  the  right-hand  spool,  increasing  the  ten- 
on. This  will  have  a  tendency  to  let  the  current  fall  much  lower 
3fore  the  armature  comes  in  contact  with  //,  to  cause  the  cur- 
;nt  to  increase.  By  simply  tapping  the  armature  G  quickly  with 

pencil  or  piece  of  wood,  forcing  it  down  with  its  contact,  and 
;  the  same  time  watching  the  ammeter,  the  current  may  be 
rought  up  to  6.8  amperes  if  6.6  amperes  is  normal,  or  9.8  if  9.6 

normal.  With  the  current  at  6.8  amperes,  which  is  .2  amperes 
igh,  the  adjusting  button  L  should  be  turned  to  increase  the  ten- 
on on  this  spring  until  the  armature  M  comes  in  contact  with 
ontact  JV,  which  will  force  current  down  through  0.  The  clutch 
hich  pulls  the  brushes  forward  and  rocks  the  rheostat  back  for 
iss  current  will  thus  be  energized.  Repeat  this  adjustment  two 
r  three  times,  but  do  not  touch  the  adjusting  button  K;  adjust 

until  it  is  just  right. 

At  the  side  of  the  armature  M  a  little  wedge  is  screwed  in  by 
leans  of  an  adjusting  button,  and  increases  or  decreases  the 
average  on  this  armature.  See  that  this  wedge  is  fairly  well  in 


118 


HANDBOOK    ON    ENGINEERING. 


CE 
LJ 


a 

cc 

a 
u 


en 

CE 
CD 


en 
o 


u 

z 

a 
u 


ou 

,0,0 


Diagram  No.    13454. 


HANDBOOK    ON    ENGINEERING.  119 

between  the  core  or  frame  of  the  spool  and  the  spring  of  the 
armature.  The  armature  M  may  have  to  be  taken  out  and  the 
spring  slightly  bent.  It  is  advisable  to  have  the  screw  which 
passes  through  the  adjuster  button  L  about  half  way  in,  to  allow 
an  equal  distance  up  and  down  for  adjusting  this  lighter  spring 
after  the  wedge-shaped  piece  is  in  the  right  position  to  give  the 
necessary  tension  on  the  spring  which  is  fastened  to  the  arma- 
ture M. 

Having-  adjusted  the  spool  /so  that  the  current  will  not  rise 
above  6.8  (or  9.8)  amperes,  move  the  armature  M  up  to  contact 
N  with  a  pencil  or  piece  of  wood,  causing  the  current  to  be  re- 
duced to  about  6.2  (or  9.2).  After  the  current  settles  at  this 
point,  decrease  the  tension  on  the  spring  which  is  fastened  to 
armature  Gr,  allowing  this  armature  to  fall  down  to  contact  H. 
Current  will  then  flow  through  Q,  which  will  rock  the  brushes 
back  and  also  move  the  rheostat  arm  for  more  current.  As  the 
spool  Jhas  been  adjusted  for  6.8  (or  9.8)  amperes,  the  current 
cannot  rise  above  that  amount,  no  matter  how  the  spool  F  js 
adjusted. 

The  Two  small  shunt  coils,  R  and  S,  are  connected  around  the 
two  contacts  simply  to  decrease  the  spark  between  the  silver  and 
platinum  contacts.  If  they  should  become  short  circuited  in  any 
way,  so  that  their  resistance  becomes  diminished,  sufficient  cur- 
rent may  pass  through  either  of  them  to  operate  the  regulator. 
If  unable  to  locate  the  trouble,  disconnect  these  coils  at  points  T 
and  U,  when  a  thorough  examination  can  be  readily  made.  M 
and  G  need  not  move  more  than  just  enough  to  open  the  con- 
tact—  -fa"  is  ample. 


120  HANDBOOK    ON    ENGINEERING. 


STARTING  THE  MULTIPOLAR  BRUSH  ARC  GENERATOR  WITH 
FORM  i  REGULATOR. 

In  starting,  the  lower  switch,  which  short  circuits  the  field 
should  be  opened  last. 

The  switch  in  the  left-hand  corner  of  the  controller  (Diagran 
No.  13454)  cuts  out  the  two  resistance  wires  which  are  used  tx 
force  the  current  through  wires  O  and  Q  to  the  clutches.  Oper 
this  switch.  Unclasp  the  brush  rocker  from  the  rheostat  rocker 
Move  the  brushes  by  hand  to  give  the  proper  spark,  allowing  th( 
rheostat  arm  to  be  moved  by  the  controller.  After  the  switches 
are  opened,  the  rhoestat  arm  will  go  clear  around  to  a  full  loac 
position,  and  then,  the  controller  takes  hold  and  brings  the  arn 
back.  In  the  meantime,  rock  the  brushes  forward  or  backwarc 
and  keep  the  spark  about  the  proper  length,  say  J"  at  full  load  t< 
|"  on  short  circuit.  Gradually  the  rheostat  arm  will  settle,  th< 
spark  will  become  constant,  and  the  machine  will  give  its  prope: 
current.  Then  clamp  the  rocker  and  rheostat  arm  together  auc 
let  the  machine  regulate  itself. 


FORM  2  REGULATOR  FOR  HULTIPOLAR  BRUSH  ARC 
GENERATORS. 

The  connections  of  the  Form  2  Regulator  are  shown  in  Fig 
10.  The  regulator  performs  two  operations ;  sweeps  a  set  o 
contacts,  throwing  •  more  or  less  resistance  in  shunt  with  th 
field  circuit,  and  at  the  same  time,  rocks  the  brushes  so  that  th 
spark  is  kept  at  proper  length,  varying  at  from  J"  at  full  load  t< 

§"  on  short  circuit. 
A  small  belt  runs  over  the  armature  shaft  M  and  drives  th 


HANDBOOK   ON    ENGINEERING. 


121 


y  oil  pump  P.     The  pump  draws  the  oil  from  the  containing 
se  and  forces  it  through  passages  to  the  valve  T. 
The  ports  overlap  this  valve  so  that  the  oil  may  flow  through 
icn  the  valve  is  in  its  central  position.     The  valve  is  controlled 
the  electromagnet  F  (Fig.  10)  which  actuates  the  armature  U 


Form  2  Regulator. 


d  the  lever  H.  The  pull  on  armature  U  varies  with  the  strength 
the  current  which  excites  F.  The  opposite  end  of  the  lever  // 
attached  to  spring  G,  which  is  adjusted  by  the  screw  nut  R  so 
to  hold  the  valve  in  central  position  when  normal  current  is 
•wing  through  the  controlling  magnet. 


122 


HANDBOOK    ON    ENGINEERING. 


Fig.    10. 


HANDBOOK    ON    ENGINEERING.  123 

If  the  current  is  too  strong,  it  pulls  down  the  armature  C7", 
raising  the  valve,  throwing  more  oil  on  the  upper  side  of  the 
circular  piston  head  S,  and  allowing  the  oil  to  run  out  from  the 
lower  side,  thus  forcing  the  piston  X  around  clockwise,  lowering 
the  current  by  moving  the  contact  arm  so  as  to  shunt  more  cur- 
rent from  the  fields,  at  the  same  time  moving  the  brushes  forward 
until  the  current  returns  to  its  normal  value. 

If  the  current  is  too  low  the  operation  is  reversed. 


ADJUSTMENT  OF  FORH  2  REGULATOR. 

To  raise  the  current,  turn  the  hard  rubber  nut  R  (Fig..  10)  to 
the  right.  If  the  current  is  too  high,  turn  the  nut  to  the  left. 

The  limits  between  which  the  regulator  operates  are  deter- 
mined by  the  number  of  turns  in  the  spring  G.  If  the  spring  G 
is  stiffened  by  cutting  off  some  of  the  turns  and  stretching  it  out, 
the  limits  of  regulation  will  be  wider.  If  the  spring  has  a  greater 
number  of  turns,  it  will  regulate  within  narrower  limits,  but  be 
more  liable  to  "  pump." 

The  regulator  may  be  caused  to  operate  quickly  in  one  direc- 
tion and  slowly  in  the  reverse  direction  by  changing  the  position 
of  the  stops  on  lever  //.  By  raising  the  stop  on  the  right-hand 
side  of  lever  J/,  the  movement  on  increasing  the  current  will  be 
retarded. 


STARTING  THE  MULTIPOLAR  BRUSH  ARC  GENERATOR  WITH 
FORM  2  REGULATOR. 

Before  starting  the  machine,  the  oil  box  of  the  regulator  should 
be  filled  with  a  light  spindle  or  dynamo  oil  nearly  up  to  the  shaft 
which  carries  the  contact  arm,  etc. 

If  the  pump  fails  to  start  promptly,  it  may  be  started  by  shift- 


124  HANDBOOK    ON    ENGINEERING. 

ing  the  brushes  backward  and  forward,  and  moving  the  contact 
arm. 

In  a  newly  installed  machine,  the  oil  should  be  changed  at 
least  once  a  week. 

Having  correctly  adjusted  the  regulator  for  the  desired  cur- 
rent, as  previously  described,  the  starting  valve  handle  /S1  (Fig. 
10)  should  be  turned  counter  clockwise  when  the  machine  is 
running  without  load.  This  handle  operates  a  valve  which  con- 
nects both  sides  of  the  circular  cylinder,  thereby  giving  a  free 
flow  of  oil  between  the  two  sides,  and  preventing  the  operation  of 
the  piston  and  relieving  the  pump  from  any  undue  loado 

To  put  the  machine  in  operation,  the  valve  should  be  gradu- 
ally thrown  around  clockwise,  cutting  off  the  flow  of  oil  from  the 
two  sides  of  the  cylinder  after  the  switches  have  been  opened. 
This  valve  may  also  be  used  to  throw  the  regulator  out  of  opera- 
tion if  desired. 

FORM  3  REGULATOR  FOR  MULTIPOLAR  BRUSH  ARC  GENE- 

RATORS. 

In  the  Form  3  Regulator  a  belt  from  the  armature  shaft  runs 
a  small  countershaft  with  crank  attached.  A  rocking  or  recipro- 
cating motion  is  thus  imparted  to  the  main  lever,  on  which  are 
pivoted  two  self-adjusting  clutch  jaws  or  grips.  When  the  cur- 
rent is  normal,  the  clutches  are  held  stationary,  but  as  the  current 
varies,  either  above  or  below  normal,  the  clutch  on  one  side  is 
dropped  so  that  it  will  grip  the  clutch  disk,  and  the  mechanism 
revolves  in  the  proper  direction  to  restore  the  current. 

With  slight  variations  of  the  current,  the  regulator  contact 
arm  is  moved  forward  or  backward  very  slowly ;  while,  with 
greater  variations,  caused  by  any  considerable  number  of  lamps 
being  cut  in  or  out,  the  movement  is  increased  and  the  normal 
point  or  position  more  quickly  reached. 


HANDBOOK    ON   ENGINEERING.  125 

For  starting  Brush  Arc  Generators  with  Form  3  Regulators, 
see  general  directions  under  Form  1  Regulator. 


FORM  4  REGULATOR  FOR  MULTIPOLAR  BRUSH  ARC  GENE- 
RATORS. 

The  Form  4  Regulator  is  similar  to  the  Form  3  ;  the  counter- 
shaft and  rocking  lever  are  identical,  but  instead  of  using  clutches, 
the  lever  operates  two  pawls,  which  engage  in  ratchet  wheels. 
The  pawls  are  not  in  contact  when  the  current  is  normal,  but  are 
thrown  in  to  move  the  arm  to  either  right  or  left  as  the  current 
varies  and  the  regulator  is  called  upon  to  shunt  more  or  less  cur- 
rent from  the  tield. 

AMMETER. 

A  reliable  ammeter  should  always  be  connected  in  the  circuit 
of  an  arc  generator,  so  that  the  exact  current  may  be  read  at  a 
glance.  It  should  be  connected  into  the  negative  side  of  the  line 
where  the  circuit  leaves  the  regulator. 

INSTRUCTIONS  FOR  INSTALLING  AND  OPERATING  inPROVED 
BRUSH  ARC  LAMPS. 

Suspension*  —  One  of  three  methods  of  suspension  may  be 
used  for  Brush  Arc  Lamps.  If  chimney  suspension,  which  is  the 
most  common,  is  adopted,  the  wire,  cable  or  rope  used  to  suspend 
the  lamp  must  be  carefully  insulated  from  the  chimney.  For  this 
purpose  a  porcelain  insulator  should  be  inserted  between  the 
support  and  the  lamp. 

Hook  suspensions  may  be  used  to  advantage  in  some  places, 
but  greater  care  must  be  taken  to  insulate  the  supporting  wires 
from  any  conductors,  as  the  hooks  form  the  terminals  of  the  lamp. 


126  HANDBOOK    ON    ENGINEERING. 

The  most  convenient  arrangement  for  indoor  use  is  to  suspend 
the  lamp  from  a  hanger  board.  The  porcelain  base  of  the  hanger 
board  prevents  short  circuits  or  grounds. 

The  lamps  run  nominally  on  circuits  of  6.6  amperes  for  1200 
candle-power  and  9.6  amperes  for  2000  candle-power.  In  case 
it  is  necessary  to  run  a  lamp  on  a  circuit  differing  from  the 
standard,  the  lamp  may  be  adjusted  by  moving  the  contact  on 
the  adjuster.  This  will  compensate  for  about  one  ampere  either 
way  from  normal  and  is  set  in  about  the  middle  position  when 
the  lamp  is  shipped. 

Permanent  adjustment  for  special  circuits  of  variation  greater 
than  one  ampere  from  standard  is  made  by  filing  the  soft  iron 
armature.  The  clutch  should  be  so  adjusted  that  the  center  of 
the  armature  is  ||"  above  the  plate  when  the  trip  on  the  first  rod 
is  touching  the  bushing  and  J£''  when  the  trip  on  the  second  rod 
is  in  a  similar  position.  A  small  gauge  is  convenient  for  adjust- 
ing the  clutch.  The  position  of  the  trip  of  the  clutch  determines 
the  feeding  point  of  the  lamp. 

After  thoroughly  repairing  and  cleaning  the  lamp,  it  should  be 
run  a  short  time  before  installing.  Lamps  should  not  be  tested  in 
an  exposed  place,  as  a  strong  draft  of  air  will  cause  unpleasant 
hissing,  which  may  be  mistaken  for  some  internal  trouble. 

Lamps  should  not  hiss  or  name  if  good  carbons,  are  used.  A 
voltmeter  should  always  be  used  when  adjusting  or  testing. 

Connecting*  —  The  lamp  terminal  hooks  are  marked  P  (posi- 
tive) and  N  (negative),  and  should  be  connected  into  circuit 
accordingly. 

The  carbons  should  rest  in  contact  when  the  lamp  is  cut  out. 
When  the  switch  is  opened,  part  of  the  current  from  the  positive 
terminal  hook  (P)  goes  through  the  adjuster  to  the  yoke,  and 
thence  through  the  carbon  rod  and  carbons  to  the  negative  ter- 
minal hook  (^).  The  remainder  of  the  current  goes  to  the  cut- 
out block,  but,  as  the  cut-out  is  closed  at  first,  the  current  crosses 


HANDBOOK    OX    ENGINEERING.  127 

over  through  the  cut-out  bar  to  the  starting  resistance,  and  so  to 
the  negative  side  of  the  lamp.  A  part  of  it,  however,  is  shunted 
at  the  cut-out  block  through  the  coarse  wire  of  the  magnets,  and 
so  to  the  upper  carbon  rod  and  carbons  and  out.  This  shunted 
current  energizes  the  magnets  and  so  raises  the  armature  which 
opens  the  cut-out  and  at  the  same  time  establishes  the  arc  by 
separating  the  carbons. 

The  fine  wire  winding  is  connected  in  the  opposite  direction 
from  the  coarse  winding,  and  its  attraction  is  therefore  opposite. 
When  the  arc  increases  in  length,  its  resistance  increases,  and 
consequently,  the  current  in  the  fine  wire  is  increased.  The 
attraction  of  the  coarse  wire  winding  is,  therefore,  partly  overcome 
and  the  armature  begins  to  fall.  As  it  falls,  the  arc  is  shortened 
and  the  current  in  the  fine  wire  decreases.  The  mechanism  feeds 
the  carbons  and  regulates  the  arc  so  gradually  that  a  perfectly 
steady  arc  is  maintained. 

The  fine  wire  of  the  magnets  is  connected  in  series  with  the 
winding  of  a  small  auxiliary  cut-out  magnet  at  the  top  of  the 
mechanism. 

This  magnet,  which  also  has  a  supplementary  coarL3  winding, 
does  not  raise  its  armature  unless  the  voltage  at  the  arc  increases 
to  70  volts.  The  two  windings  connect  at  the  inside  terminal 
on  the  lower  side  of  the  auxiliary  cut-out  magnet,  and  the  current 
from  the  fine  wire  of  the  main  magnets  passes  through  both  wind- 
ings and  then  to  the  cut-out  block  and  so  to  the  starting  resist- 
ance and  out. 

If  the  main  current  through  the  carbon  is  interrupted  (as  by 
breaking  of  the  carbons),  the  whole  current  of  the  lamp  passes 
through  the  fine  wire  circuit.  Before  this  excessive  current  has 
time  to  overheat  the  fine  wire  circuit,  it  energizes  the  auxiliary 
cut-out  magnet  and  closes  a  circuit  directly  across  the  lamp 
through  the  coarse  wire  on  the  auxiliary  cut-out  to  the  main  cut- 
out block,  and  thence  to  the  negative  terminal. 

The  auxiliary  cut-out  operates  instantly  and  prevents  any  dan- 


128 


HANDBOOK    ON    ENGINEERING. 


ger  to  the  magnets  during  the  short  period  required  for  the  main 
armature  to  drop  and  throw  in  the  main  cut-out.     When  the  main 


CONNECTIONS  FOR  IMPROVED  BRUSH  ARC  LAMPS. 

cut-out  operates,  the  armature  of  the  auxiliary  cut-out  fails,  because 
there  is  not  sufficient  current  in  that  circuit  to  energize  the  magnet. 


HANDBOOK    ON    ENGINEERING.  129 

The  voltage  at  which  the  auxiliary  cut-out  magnet  operates 
depends  on  the  position  of  its  armature,  which  is  regulated  by 
the  screw  securing  the  armature  in  position.  It  should  not  be 
adjusted  to  operate  at  less  than  70  volts. 

The  carbons  should  be  solid  and  of  uniform  quality.  For  the 
best  results,  the  upper  carbon  should  be  12"  xT7^",  and  the 
lower  7"x  •£-$".  The  stub  of  the  upper  carbon  may  then  be  used 
in  the  lower  holder  when  retrimming. 

At  each  trimming  the  rod  should  be  carefully  wiped  with 
clean  cotton  waste.  It  should  never  be  pushed  up  into  the  lamp 
in  a  dirty  condition. 

In  order  to  remove  the  carbon  rod  or  examine  the  mechanism,  the 
jacket  must  be  lowered  by  pressing  a  spring  clip  on  its  under  side. 

The  carbon  rod  may  be  unscrewed  and  removed  by  a  small 
screw-driver  or  small  strip  of  metal  inserted  in  the  slot  cut  in  the 
rod  cap.  The  cap  will  remain  in  the  hole  through  the  yoke  when 
the  rod  is  taken  out. 

The  lamp  must  never  be  left  burning  with  the  jacket  off,  nor 
be  allowed  to  hang  with  the  mechanism  exposed  to  the  weather. 

PERSONAL  SAFETY. 

Never  allow  the  body  to  form  part  of  a  circuit.  While  hand- 
ling a  conductor,  a  second  contact  may  be  made  accidentally 
through  the  feet,  hands,  knees  or  other  part  of  the  body  in  some 
peculiar  and  unexpected  manner.  For  example,  men  have  been 
killed  because  they  touched  a  "live"  wire  while  standing  or 
sitting  upon  a  conducting  body. 

Rubber  gloves  or  rubber  shoes,  or  both,  should  be  used  in 
handling  circuits  of  over  500  volts.  The  safest  plan  is  not  to 
touch  any  conductor  while  the  current  is  on,  and  it  should  be 
remembered  that  the  current  may  be  present  when  not  expected, 
due  to  an  accidental  contact  with  some  other  wire  or  to  a  change 

9 


130 


HANDBOOK    ON    ENGINEERING. 


of  connections.     Tools  with  insulated  handles,  or  a  dry  stick  of 
wood,  should  be  used  instead  of  the  bare  hand. 

The  rule  to  use  only  one  hand  when  handling  dangerous  elec- 
trical conductors  or  apparatus  is  a  very  good  one,  because  it 
avoids  the  chance,  which  is  very  great,  of  making  contacts  with 
both  hands  and  getting  the  full  current  right  through  the  body. 
This  rule  is  often  made  still  more  definite  by  saying,  "  Keep  one 
hand  in  your  pocket, ' '  in  order  to  make  sure  not  to  use  it.  The 
above  precautions  are  often  totally  disregarded,  particularly  by 
those  who  have  become  careless  by  familiarity  with  dangerous 
currents.  The  result  of  this  has  been  that  almost  all  the  persons 
accidentally  killed  by  electricity  have  been  experienced  electric 
linemen  or  stationmen. 


TABLE     SHOWING    RELATIVE    RESISTANCE    OF     METALS     AT    TEMPERA- 
TURE   OF    70    DEGREES    F. 


NAME  OP  METAL. 

Resistance  in  Ohms  of  Wire  100  ft.  long  and 
one-thousandths  of  an  inch  in  diameter. 

Silver  

965 
1,030 
1,328 
1,900 
3,600 
5,700 
6,400 
7,500 
8,500 
12,600 
12,700 
23,000 
42,000 
57,700 
3,792,000 

Remarks. 

The  resistance  of  arc  light  car- 
bons is  given  for  comparison  and, 
as  will  be  noticed,  it  is  about 
4000  times  as  great  as  that  of 
silver. 

To  obtain  the  resistance  of 
100  ft.  of  wire  of  any  size,  divide 
the  figures  in  this  table  by  the 
square  of  the  diameter  of  the 
wire  in  thousandths  of  an  inch. 

Copper  

Gold  

Aluminum  

Zinc      

Platinum  

Iron   \Vrought  

Nickel    

Tin  

German  Silver  

Lead  .        

Antimony  

Manganese  Steel.... 
Mercury  

Arc  Light  Carbon  .. 

HANDBOOK    ON    ENGINEERING. 


131 


Fig.  1.     The  Thomson-Houston  Standard  Arc  Dynamo 
Arranged  for  Right-hand  Rotation, 


CHAPTER    X. 
INSTALLATION  OF  ARC  DYNAMOS. 

Location  and  mounting*  —  The  generator  should  be  located 
in  a  cool,  dry  room,  free  from  dust,  metal  chips  or  flying  parti- 
cles of  any  sort.  Space  should  be  allowed  around  the  machine 
to  give  ample  room  for  reaching  all  parts  of  it,  particularly  the 
commutator.  The  generator  should  be  set  upon  a  firm  founda- 


132  HANDBOOK    ON    ENGINEERING. 

tion  of  well-seasoned  wood,  and  should  be  mounted  upon  a 
sliding  bed-plate,  so  that  the  belt  can  be  tightened  or  loosened 
while  the  generator  is  running.  The  generator  should  be 
thoroughly  insulated  from  earth.  The  sliding  bed-plates  as  now 
manufactured  are  designed  to  provide  perfect  insulation,  and 
meet  this  requirement  fully.  The  direction  of  rotation  of  the 
armature  in  the  standard  generator  is  from  right  to  left,  or 
counter-clockwise,  as  seen  when  facing  the  commutator.  This  is 
called  a  right-hand  machine.  Right-hand  machines  may  be  run 
left-handed  by  replacing  certain  parts  of  the  brush-holder  'and 
regulating  mechanism. 

Pulleys*  —  The  generator  is  provided  with  a  pulley  of  proper 
size  to  transmit  the  power  demanded. 

Bearings*  —  The  oil  in  the  reservoir  should  be  renewed  once  a 
week  for  the  first  two  or  three  weeks. 

Speed*  —  The  generator  should  be  run  as  nearly  as  possible  at 
the  speed  given  by  the- maker.  An  increase  of  speed,  if  not  too 
excessive,  will  'do  no  harm,  but  a  considerable  diminution  in 
speed  below  normal,  when  the  generator  is  doing  its  maximum 
work,  is  liable  to  cause  unsteadiness  in  the  lights. 

The  automatic  regulator  will  adjust  perfectly  for  fluctuations 
in  speed  near  or  above  normal,  unless  the  fluctuations  are 
extremely  sudden,  as  in  the  case  of  slipping  of  the  belt. 

Belts* — The  belt  should  be  about  half  an  inch  narrower  than 
the  face  of  the  pulley.  An  endless  belt  is  desirable. 

Brushes*  —  When  the  generator  is  in  position  the  brushes  or 
strips  of  copper  B  B,  Bl  Bl  (see  Fig.  3),  are  placed  on  the 
machine  in  the  manner  shown.  All  four  brushes  should  be  set 
exactly  to  the  gauges  sent  with  each  machine,  so  that  they  press 
with  sufficient  force  on  the  surface  of  the  commutator  to  insure 
good  contact  at  all  times. 

The  length  of  the  gauge  is  such  that  the  brushes  project  a 
little  past  the  center  of  the  commutator,  as  shown  in  Fig.  5,  to 


HANDBOOK    ON    ENGINEERING. 


133 


oooooo   oooooo 
oooooo   oooooo 


CONNECTIONS  FOR  ARC  LIGHTING  SYSTEM. 

Fig.  2. 


134 


HANDBOOK   ON   ENGINEERING. 


avoid  catching  in  the  slots  should  the  armature  be  turned  back- 
ward. 

Air  Blast*  —  The  air  blast  or  blower  plays  an  important  part 
in  the  successful  operation  of  the  machine.  The  air  blast  requires 
no  attention,  except  that  it  should  be  kept  scrupulously  clean  and 
well  oiled.  Only  the  best^quality  of  mineral  oil  should  be  used. 
Poor  oil  will  always  cause  trouble. 

The  screens  which  cover  the  air  inlets  on  the  air  blast,  should 


r  ,  CONNECTIONS  FOR  RHEOSTAT. 

Fig.  3. 

be   kept   clean  and  free  from  dust.     They  should  be  taken  out 
about  once  a  month  and  cleaned  in  kerosene  oil. 

Regulator*  —  The  regulator  is  fastened  to  the  frame  of  the 
machine  by  two  short  bolts,  as  shown  in  Fig.  2.  On  the  left- 
hand  machine,  i.  e.,  one  which  runs  clockwise,  its  position  is  on 
the  opposite  side.  Before  filling  the  dash-pot  D  with  glycerine, 
see  that  the  regulator  lever  and  its  connections,  brush  yokes,  etc., 
are  free  in  every  joint,  and  that  the  lever  L  can  move  freely  up 
and  down.  Then  fill  the  dash-pot  D  with  concentrated  glycerine. 


HANDBOOK:  ON  ENGINEERING. 


135 


The  long  wire  from  the  regulator  magnet  M,  is  connected  with 
the  left-hand  binding  post  P  of  the  machine,  and  the  short  wire 
with  the  post  P2  on  the  side  of  the  machine.  The  inside  wire 
of  the  field  magnet,  or  that  leaving  the  iron  flange  of  the  left-hand 
field  should  be  connected  into  the  post  P2  also,  as  shown  in  Fig. 
2.  The  electric  circuit  (see  Fig.  3),  should  be  complete  from 


CONTROLLER  FOR  ARC  DYNAMO. 

Fig.  4. 

P1  on  the  controller  magnet,  through  the  lamps  to  post  N"  on  the 
machine,  through  the  right-hand  field  magnet  O1,  to  the  brushes 
B1  B1,  through  the  commutator  and  armature  to  the  brushes 


136  HANDBOOK    ON    ENGINEERING. 

B  B,  through  the  left-hand  field  C,  to  posts  P2  and  P,  thence  to 
posts  P2  and  P  on  the  controller  magnet,  through  the  controller 
magnet  to  P1.  The  current  passes  in  the  direction  indicated  by 
the  arrows. 

Controller.  —  The  controller  magnet  (see  Fig.  4)  is  to  be  fast- 
ened securely  by  screws  to  the  wall  or  some  rigid  upright  support, 
taking  care  to  have  it  perfectly  plumb.  It  is  connected  to  the 
machine  in  the  manner  shown  in  Fig.  3,  i.  e.,  the  binding  post 
P2  on  the  controller  magnet,  is  connected  to  the  binding  post  P2 
(see  Fig.  2)  on  the  end  of  the  machine ;  and  likewise,  the  post 
P  on  the  controller  to  the  post  P  on  the  leg  of  the  machine  ;  the 
post  P1  forms  the  positive  terminal  from  which  the  circuit  is  to 
run  to  the  lamps  and  back  to  AT. 

Great  care  should  be  take-  to  see  that  wires  P  P  and  P2  P2 
are  fastened  securely  in  place ;  for  if  the  connection  between  P 
and  P  should  be  impaired  or  broken,  the  regular  magnet  M  would 
be  thrown  out  of  action, 'thus  throwing  on  the  full  power  of  the 
machine,  and  if  the  wires  P2  P2  should  become  loosened,  the  full 
power  of  the  magnet  M  would  be  thrown  on,  and  the  regulator 
lever  L,  rising  in  consequence,  would  greatly  weaken  or  put  out 
the  lights. 

The  wires  leading  from  the  controller  magnet  to  the  machine 
should  have  an  extra  heavy  insulation.  Care  should  be  taken  in 
putting  up  the  controller  magnet  that  the  following  directions  are 
followed :  — 

(1)  The  cores  B  of  the  axial  magnets  C  C  must  hang  exactly 
in  the  center,  and  be  free  to  move  up  and  down. 

(2)  The  screws  fastening  the  yoke  or  tie    pieces  to  the  two 
cores  must  not  become  loosened. 

(3)  The  contacts  0  must  be  firmly  clos'ed  when  the  cores  are 
not  attracted  by  the  coils  C  O,  which  is  the  case,  of  course,  when 
no  current  is  being  generated  by  the  machine,  and  when  the  cores 


HANDBOOK    ON    ENGINEERING.  137 

are  lifted,  the  contacts  must  open  from  fa"  to  -fa"  ;  a  greater 
opening  than  ^y  has  the  effect  of  lengthening  the  time  of  action 
of  the  regulator  magnet.  This  tends  to  render  the  current  un- 
steady, and  in  case  of  a  very  weak  dashpot  or  short  circuit,  might 
cause  flashing.  If  this  adjustment  is  not  properly  made  there 
will  be  destructive  sparking  on  a  small  portion  of  the  contact  sur- 
faces. 

(4)  All  connections  must  be  perfectly  secure. 

(5)  The  check-nuts  ^/"must  be  tight. 

(G)  The  carbons  in  the  tubes  L  must  be  whole. 

These  carbons  form  a  permanent  shunt  of  high  resistance 
around  the  regulator  magnet  jfef,  and  if  broken  will  cause  destruc- 
tive sparking  at  contacts  0,  burning  them  and  seriously  interfer- 
ing with  close  regulation  of  the  generator.  In  case  a  carbon 
should  become  broken,  temporary  repairs  may  be  made  by  splic- 
ing the  broken  piece  with  fine  copper  wire.  To  keep  the  action 
of  the  controller  perfect,  the  contacts  0  should  be  occasionally 
cleaned  by  inserting  a  folded  piece  of  fine  emery  cloth  and  draw- 
ing it  back  and  forth. 

The  amount  of  current  generated  by  each  machine  depends 
upon  the  adjustment  of  the  spring  S.  If  the  tension  of  this 
spring  is  increased,  the  current  will  be  diminished  ;  if  the  tension 
is  diminished,  the  current  will  be  increased. 

Once  set  up  and  in  perfect  working  condition,  adjusted  to  the 
proper  current,  the  controller  magnet  should  rarely  need  any 
adjustment. 

Testing  arc  light  dynamos.  —  The  commutator  should  lit  the 
shaft  snugly,  but  be  sufficiently  free  to  turn  easily  on  the  shaft. 
Be  very  careful  to  put  the  short  brush-holders  on  the  outer  yoke, 
and  the  long  brush-holders  on  the  inner  yoke.  Also  see  that  the 
long  binding  post,  attached  to  the  sliding  connection,  is  on  the 
lower  left-hand  brush-holder,  and  the  short  post  on  the  lower  right- 


138 


HANDBOOK    ON    ENGINEERIEG. 


r 


A  —  Commutator  Segments. 
g4.  |  Primary  Brushes. 

B1 ) 

g« }  Secondary  Brushes. 


C — Forward  Point  of  Segment. 
D— Point  of  Brush. 
E— Brush-holders. 
F— Point  of  Contact, 


Figs.  5  and  6. 


^HANDBOOK   ON   ENGINEERING.  139 

hand  brush-holder.  Always  set  the  brush-holders  to  the  proper 
angle  by  the  brush-holder  gauge.  First  tighten  up  the  brush-hold- 
ers and  then  turn  them  to  the  correct  position  by  means  of  a  piece 
of  steel  wire  passed  through  the  holes.  Then  permanently  tighten 
up  the  brush-holders  very  firmly,  trying  them  with  the  gauge  to 
see  that  they  are  the  same  distance  from  the  commutator.  Always 
be  careful  to  get  the  brushes  exactly  straight  and  flat  before 
clamping  them  to  the  brush-holders,  and  always  set  them  to  the 
exact  length  of  the  brush  gauge. 

Setting  the  cut-out*  —  After  the  brushes  are  in  position,  the 
cut-out  must  be  set.  This  is  done  by  turning  the  commutator  on 
the  shaft  in  the  direction  of  rotation  (if  the  commutator  is  set  in 
position  the  whole  armature  must  be  revolved),  until  any  two  seg- 
ments are  just  touching  the  primary  brush  on  that  side,  as  seg- 
ments A'  and  A"  '  touch  brush  Bl  in  Fig.  6.  Under  these 
conditions  brush  B4  should  be  at  the  left-hand  edge  of  upper 
segment.  Then  turn  commutator  until  the  same  two  segments  are 
just  touching  brush  B2,  when  the  end  of  brush  Bs  should  just 
come  to  the  right-hand  edge  of  the  lower  segment.  If  the  second- 
ary brush  projects  beyond  the  edge  of  the  segment  the  regulator 
arm  should  be  bent  down ;  if  it  does  not  come  to  the  edge  of  the 
segment  the  arm  should  be  bent  up. 

Care  must  be  taken  that  the  regulator  armature  is  down  on  the 
step  when  the  cut-out  is  being  set. 

Always  try  the  cut-out  on  both  primary  brushes.  If  it  does 
not  come  the  same  on  both,  turn  one  over.  If  the  brush-holders 
are  correctly  set  by  the  gauge,  there  should  be  no  trouble  in  get- 
ting the  cut-out  set  properly  after  one  or  two  trials. 

The  distance  from  the  tip  of  the  brush,  which  is  on  top,  to  the 
left-hand  edge  of  No.  2  segment  on  a  right-hand  machine,  or  to 
the  right-hand  edge  of  No.  3  segment  in  a  left-hand  machine,  is 
called  the  lead,  and  should  be  made  to  correspond  to  the  follow- 
ing table :  — 


140  HANDBOOK    ON    ENGINEERING. 


TABLE  OF  LEADS. 

DRUM  ARMATURES.  RING  ARMATURES. 

C12  i"  positive.  K12  TV'  positive. 

C2  I"         "  K2  i"          " 

E12  Ty      "  M12  i"  negative. 

E2  1"  u  M2J"  " 

H12  I"       "  LD12  J"  positive. 

H2  J"         "  LD2i"        " 


MD2 


Place  the  screws  in  the  binding  posts  at  the  lower  ends  of  the 
sliding  connections  and  put  on  the  dash-pot  connections  between 
the  brashes,  with  the  heads  of  the  connecting  screws  outward. 
In  every  case  the  barrel  part  of  the  dash-pot  is  connected  to  the 
top  brush-holder,  and  plunger  part  to  the  bottom  brush-holder. 
See  that  the  field  and  regulator  wires  are  connected  and  that  all 
connections  are  securely  made.  When  all  connections  have  been 
made,  make  a  careful  examination  of  screws,  joints,  and  all  mov- 
ing parts.  They  must  be  free  from  stickiness,  and  not  bind  in 
any  position. 

To  determine  when  the  machine  is  under  full  load,  notice  the 
position  of  the  regular  armature,  which  should  be  within  J"  of 
the  stop.  At  full  load  the  normal  length  of  the  spark  on  the  com- 
mutator should  be  about  T3/'  .  If  it  is  less  than  this,  shut  clown 
the  machine  and  move  the  commutator  forward,  or  in  direction  of 
rotation  until  the  spark  is  of  the  desired  length.  If  the  spark  is 
too  long,  move  the  commutator  back  the  proper  amount. 


HANDBOOK    ON    ENGINEERING. 


141 


BEST  POSITION  OF  AIR   BLASTS  .AND  JETS  ON 
LD  AND  MD  DYNAMOS. 


Lift  Regulator  as  high  as  possible. 
Figs.  7  and  8. 


142  HANDBOOK   ON   ENGINEERING. 


DIRECTIONS  FOR  SETTING  THE  AIR  BLAST  JETS  ON  LD  AND 
MD  DYNAMOS. 


With  new  segments*  —  Loosen  bolts  A— A— A— A  and  turn  the 
air-blast  so  as  to  bring  the  bolts  in  the  centers  of  the  slots 
B-B-B-B.  Set  the  brushes  by  the  gauge.  Lift  the  regulator 
lever  as  high  as  possible  and  set  the  point  D  of  the  air  blast  jet 
^"  in  front  of  the  point  P  of  the  brush  A.  Place  the  lower  jet 
in  the  same  relative  position  with  the  lower  brush. 

As  segments  wear  down. —  Loosen  the  bolts  A-A-A-A  and 
follow  up  the  wear  of  the  segments  by  turning  the  air  blast  against 
direction  or  rotation  of  armature  as  indicated.  Turn  the  point 
of  the  jet  downward,  so  as  to  blow  more  directly  through  the  slot 
between  the  segments.  Set  the  lower  jet  in  the  same  relative 
position  with  the  lower  "brush. 


SOME  TROUBLES  WHICH  MAY  BE  HET  AND  THEIR 
CAUSES  — REVERSAL  OF  POLARITY. 


Cases  are  frequently  reported  where  generators,  from  lightning 
discharges,  wrong  plugging  on  switch-board,  or  some  other 
reason,  suffer  a  reversal  of  polarity.  The  effect  of  reversal  is 
that  the  lamps  in  circuit  with  the  machine  burn  u  upside  down  ;  " 
which  has  the  effect  of  throwing  much  of  the  light  up  instead  of 
down,  and  with  some  carbons  the  arc  will  flame  badly.  This  can 
be  remedied  temporarily,  by  changing  the  plugs  on  the  switch- 
board, so  that  the  current  will  enter  the  line  where  ordinarily  it 
returns. 

Occasion  should   be   taken,    however,    as    soon   thereafter   as 


HANDBOOK    ON    ENGINEERING.  143 

possible,  to  properly  magnetize  the  fields  so  that  they  will  be  the 
right  polarity,  as  follows  :  — 

Close  the  armature  short  circuiting  switch  on  the  frame  of  the 
machine  and  run  a  loop  from  some  other  arc  generator  which 
happens  to  be  in  operation.  Connect  the  positive  side  of  this  loop 
to  the  lower  binding  post  JV  on  the  right  leg  of  the  machine,  and 
the  negative  side  of  the  binding  post  I*2  on  the  end  of  the  frame 
under  the  regulator.  Then  open  the  armature  short  circuiting 
switch  on  the  second  generator.  A  very  few  seconds  will  suffice 
to  correctly  polarize  the  first  machine. 

To  detect  a  short  circuit  in  the  field,  make  all  adjustments  as 
if  working  under  normal  conditions,  then  run  the  machine  at  the 
proper  speed  on  a  dead  short  circuit.  If  there  is  no  short  circuit 
in  the  field,  the  armature  of  the  regulator  will  be  drawn  up  hard 
against  the  bottom  of  the  magnet,  but  if  there  is  a  short  circuit  in 
the  field  the  armature  will  drop  more  or  less  according  to  the 
amount  of  field  wire  cut  out  of  circuit. 

To  find  out  which  half  of  the  field  is  affected,  close  the  field 
switch  and  remove  the  regular  wire  from  the  Post  P2,  Fig.  2,  then 
connect  posts  P2  and  N  to  some  source  of  direct  current,  as  a 
110-volt  exciter,  and  with  a  volt-meter  measure  the  drop  in 
voltage  between  posts  N  and  A1  and  between  A  and  P2.  The 
drop  should  be  very  nearly  the  same  in  both  cases  if  the  winding 
is  perfect,  but  the  drop  will  be  less  across  that  field  which  is 
short  circuited. 

Another  trouble  which  is  liable  to  be  met  in  flashing.  When  a 
generator  flashes  an  arc  is  drawn  around  the  commutator  from 
one  brush  to  the  other,  which  soon  short  circuits  the  armature, 
putting  out  the  lights.  This  arc  is  usually  broken  very  quickly, 
but  the  flashing  may  be  repeated  at  frequent  intervals.  There 
are  several  causes  of  flashing,  such  as  overload,  low  speed,  stick- 
iness in  the  regulating  mechanism,  short  circuit  in  the  field,  com- 
mutator not  in  proper  position,  or  a  dash-pot  which  is  too  stiff  or 


144 


HANDBOOK    ON    ENGINEERING. 


too  loose.  If  a  machine  flashes  when  running  under  proper  load 
and  at  proper  speed,  see  that  there  is  no  stiffness  in  the  regulating 
mechanism,  then  examine  the  cut-out  and  note  the  length  of  the 
spark,  which  should  be  about  T3^-"  long  at  full  load. 

If  all  these  adjustments    are   right,  make  the  test   described 
above  for  a  short  circuit  in  the  fields. 


RING  ARMATURES. 


All  K,  M,  LD  and  MD  machines  are  now  made  with  ring 
armatures. 

A  recent  improvement  in  the  construction  of  these  armatures 
consists  in  the  removal  of  all  insulation  from  the  cores  and  the 
addition  of  more  insulation  to  the  separate  coils.  The  cores  are 
divided  into  three  sections  with  ventilating  spaces  between- 


Armature  Core  and  Winding. 
Fig.  9. 

By  removing  the  insulation  from  the  cores  these  new  coils  may  be 
applied  to  any  of  the  older  armatures  now  in  use. 


HANDBOOK    ON    ENGINEERING. 


145 


In  case  it  becomes  necessary  to  remove  a  faulty  coil,  the  follow 
ing  directions  should  be  carefully  followed :  - 


Armature  Spider  and  Shaft. 
Fig.  10. 


DIRECTIONS    FOR    PLACING  COILS  IN  RING  ARMATURE 
WITH  INSULATED  CORE. 


After  the  armature  lias  been  taken  out  of  the  machine,  remove 
the  brass  binding  wire  by  cutting  the  bands,  carefully  covering 
all  the  exposed  parts  of  the  armature  with  a  cloth,  so  as  to  pre- 
vent filings  from  lodging  on  the  winding.  Remove  the  cord 
and  the  tape  from  the  joints  of  the  lead  wires  and  cross  connec- 
tions, at  each  end  of  the  armature.  Take  out  the  lead  wires  and 
remove  the  wooden  disks  from  the  shaft.  These  disks  are  held 
in  place  by  a  set-screw,  passing  through  a  brass  piece  let  into  the 
disk,  and  resting  on  the  shaft.  Unsolder  the  joints  on  the  coils 
that  are  to  be  removed.  Take  out  the  bolts  holding  the  two 
gun-metal  spiders  together,  and  with  a  long  steel  pin  or  drift, 
drive  out  the  key,  which  fastens  the  loose  spider  to  the  shaft. 
The  spider  next  to  the  pulley  is  securely  fastened  to  the  shaft  by 
a  steel  pin  drawn  tightly  into  a  reamed  hole,  passing  through 

10 


146  HANDBOOK    ON    ENGINEERING. 

both  spider  and  shaft.  By  driving  on  the  commutator  end  of  the 
shaft  with  a  hard-wood  block  and  mallet,  or  lead  hammer  the 
shaft  with  the  fixed  spider  may  be  removed,  and  the  remaining 
loose  spider  can  then  be  driven  out  with  the  hard-wood  block  and 
mallet.  Before  removing  the  shaft  and  spiders  note  the  position 
of  the  wedge  in  the  armature  core,  its  position  is  always  indicated 
by  the  letter  W  plainly  stamped  on  the  hub  of  the  loose  spider. 

Remove  the  wood  spacing  blocks,  slip  the  coils  around  on 
the  core  until  the  imperfect  coils  are  over  the  wedge,  then  spread 
these  coils  apart  so  as  to  expose  the  wedge  and  cut  away  the  insu- 
lation on  the  core  for  a  space  of  3J"  on  top  and  bottom  over  the 
space  containing  the  wedge ;  the  wedge  may  then  be  driven 
towards  the  center  of  the  core,  taking  care  that  it  does  not 
drop  on  the  coils  opposite  and  injure  them.  The  faulty  coils 
may  now  be  removed,  new  ones  be  inserted  and  the  wedge 
be  replaced  and  very  carefully  reinsulated.  This  insulation  is  put 
on,  beginning  with  the- layer  next  to  iron  core,  as  follows :  — 

(1)  1  layer  of  paper,  (5)  1  layer  of  mica, 

(2)  1  layer  of  mica,  (6)  1  layer  of  canvas, 

(3)  1  layer  of  sheeting,  (7)  1  layer  of  tape, 

(4)  1  layer  of  tape,  (8)  1  layer  of  paper. 

Slip  the  coils  around  to  their  proper  places  so  that  they  will 
be  in  correct  position  with  regard  to  the  arms  of  the  spiders. 

The  loose  spider  may  now  be  put  in  place,  and  afterwards  the 
fixed  spider  and  shaft,  the  bolts  being  inserted  and  the  nuts 
tightened  up.  Replace  the  key  in  the  loose  spider,  put  on  the 
wooden  disks  and  carefully  solder  and  tape  all  the  joints  of  lead 
wires  and  cross  connections.  Replace  the  spacing  blocks  in  their 
proper  positions,  solder  and  tape  the  connections,  and  the  arma- 
ture is  ready  to  be  bound. 


HANDBOOK    ON    ENGINEERING. 


147 


The  binding  wire  used  is  No.  11,  hard  brass.  The  arrange- 
ment of  the  binding  wire  is  clearly  shown  in  the  original  bands  of 
the  armature  and  should  be  carefully  noted  before  they  are 
removed.  The  same  brass  clips  may  be  used  again,  provided  due 
care  is  taken  in  bending  up  the  ends,  when  the  old  band  is  taken  off. 


SB 


Standard  Plug  Switchboard  for  6  Ckcuits. 
Fig.  11. 


SWITCHBOARDS. 


The  standard  arc  lighting  switchboard  consists  of  a  marble 
panel,  to  the  back  of  which  the  conductors  are  attached.  When 
very  large  boards  are  built  they  are  made  by  combining  several 
panels.  Switchboards  of  any  capacity  can  be  constructed  without 


148 


HANDBOOK    ON    ENGINEERING. 


difficulty.     The  general  arrangement  of  conductors  is  the  same 
for  all  sizes. 

Each  panel  is  drilled  with  counter-sunk  holes  arranged  in 
rows,  and  in  each  hole,  a  brass  bushing  is  fitted.  All  the  bush- 
ings of  the  same  horizontal  row  on  the  right  of  the  center  of  the 
panel  are  electrically  connected,  except  those  of  the  bottom  row, 
and  a  similar  connection  is  made  between  the  bushings  on  the 
left  of  the  center.  A  heavy  brass  strap  is  supported  by  the  back 
of  the  panel  behind  each  vertical  row  of  holes  and  has  bushings 
in  it  corresponding  to  those  in  the  face  of  the  panel.  These  straps 
are  placed  several  inches  back  of  the  marble,  but  any  one  of  them 
can  be  put  in  electrical  connection  with  any  horizontal  conductor  it 
crosses  by  the  use  of  suitable  brass  plugs  inserted  in  the  bushings. 
In  a  standard  panel  the  number  of  horizontal  rows  of  holes 

equals  one  more  than  the 
number  of  generators.  The 
vertical  rows  are  always  twice 
the  number  of  generators. 
The  positive  leads  of  the 
generators  are  attached  to 
binding  posts  on  the  left- 
hand  ends  of  the  horizontal 
conductors.  The  negative 
leads  are  connected  to  the 
corresponding  binding  posts 
at  the  right-hand  end  of  the 
board. 

The  positive  line  wires 
are  connected  to  the  vertical 
straps  on  the  left,  and  the 

-negative  wires  to  similar  straps  on  the   right  of  the  center  of  the 
panel, 

If  a  switchboard  plug  be%iuserted  in  any  of  the  holes  of  the 


Back  of  Switchboard, 
Fiff.   12. 


HANDBOOK    ON    ENGINEERING. 


149 


board,  it  puts  the  corresponding  generator  lead  and  line  wire  in  elec- 
trical connection,  but  as  the  positive  line  wires  are  back  of  the 
positive  generator  leads  only,  it  is  not  possible  to  reverse  the 
connection  of  the  line  and  generator  accidentally,  though  any 
other  combinations  of  lines  and  generators  can  be  made  readily 
and  quickly. 

The  holes  of  the  lower  horizontal  row  have  bushings  connected 


ffi 

r\ 

i 

T 

F 

m 

w 

Ifr 

1 

Star-ting 
Res  i  stance 


mam  Resists    ce 


Geoer-ator 


METER  FOR  STATION  USE. 
CONNECTIONS  FOR  WATT-METERS  FOR  SERIES  ARC  CIRCUITS 

Fig.   13. 

with  the  vertical  straps  only.  Plugs  connected  in  pairs  by  flexible 
cable  and  inserted  in  the  holes  put  the  corresponding  vertical 
straps  in  connection  as  needed,  and  normally  independent  lines 
may  be  connected  when  one  generator  is  required  to  supply 
several  circuits. 

Lines  and  generator  leads  may  be  transferred,  while  running, 


150 


HANDBOOK   ON    ENGINEERING. 


by  the  use  of  these  cables,  without  shutting  down  the  machines 
or  extinguishing  lamps. 

WATT  METERS. 

Watt-meters  are  now  built  to  measure  the  power  supplied  on 
series  arc  circuits.     These  watt-meters   are   similar  in   principle 


Interior  of  M  Arc  Lamp. 
Fig.   14. 

to  those  used  on  incandescent  lighting  systems,  and,  being  ex- 
tremely  accurate,    are   equally   effective  in  preventing  waste  of 


HANDBOOK    ON    ENGINEERING.  151 

current.  The  watt-meters  supplied  to  customers  are  made  in  4 
lamp  or  8  lamp  capacities.  An  excess  of  voltage  equivalent  to 
two  lamps  over  the  rated  load  causes  the  meter  to  automatically 
cut  out,  both  lamps  and  meters  being  short-circuited.  This  pre- 
vents the  interruption  of  the  series  circuit  in  case  of  any  local 
trouble  with  lamps  or  line  inside  the  meter  circuit.  Station  watt- 
meters are  arranged  to  measure  the  total  output  of  a  generator, 
and  are  made  with  capacities  for  35,  50,  65,  80,  125  or  150  lamps. 


INSTRUCTIONS  FOR  THE  INSTALLATION  AND  CARE  OF  ARC 

LAMPS. 


The  lamps  should  be  hung  from  the  hanger  boards  provided 
with  each  lamp,  or  from  suitable  supports  of  wire  or  chain. 

As  the  hooks  on  the  lamp  form  also  its  terminals,  they  should 
be  insulated,  where  a  hanger  board  is  not  used,  from  the  chains 
or  wires  used  to  support  the  lamp. 

To  make  the  upper  carbon  positive  the  wire  from  the  positive 
terminal  of  the  machine  should  be  fastened  into  the  binding  post- 
hook,  on  the  switch  side  of  the  D  lamp,  and  on  the  opposite  side 
in  the  M  and  K  lamps.  When  the  lamps  are  hung  where  they 
are  exposed  to  the  weather,  they  should  be  covered  with  a  metal 
hood,  to  prevent  injury  from  rain  or  snow.  In  such  cases  care 
should  be  taken  that  the  circuit  wires  do  not  form  a  contact  on 
the  metal  hood,  and  short-circuit  the  lamp.  Before  the  lamps 
are  hung  up  they  should  be  carefully  examined  to  see  that  the 
joints  are  free  to  move,  and  that  all  connections  are  perfect. 

No  lamp  should  be  allowed  to  remain  in  circuit  with  the 
covers  removed  and  mechanism  exposed.  Such  practice  is 
dangerous. 


152 


HANDBOOK   ON   ENGINEERING. 


STARTING  THE  LAMPS. 

When  the  lamps  are  all   in  position  and  ready  for  operation 
the  machine  may  be  started,  and  when  the  armature  has  reached 

P  <3>  , ,  <S   N 


CONNECTIONS  FOR  M  AND  K  ARC  LAMPS. 

Fig.   15. 

its  proper  speed,  the  short-circuiting  switch  on  the  frame  should 
be  opened. 


HANDBOOK    ON    ENGINEERING.  153 

This  method  allows  the  generator  to  take  up  its  load 
gradually,  and  is  a  very  important  point  in  the  handling  of  the 
machine,  particularly  when  series-incandescent  lamps  are  in  the 
circuit. 

The  generator  should  be  driven  at  its  proper  speed,  as  desig- 
nated by  the  maker.  The  regulator  lever  will  first  rise  and  then 
oscillate  slowly  up  and  down  for  short  distances,  as  the  regulator 
is  cut  in  and  out  by  the  controller  magnet.  If  the  movements  are 
too  great,  the  lights  will  vary  in  intensity —  first  up,  then  down. 
This  condition  will  result  from  a  weakness  of  the  regulator  dash- 
pot.  The  regulator  lever  should  always  be  a  short  distance  away 
from  the  stop  —  say  from  |"  to  |-"  or  more,  according  to  condi- 
tions —  and  should  always  vibrate  up  and  down  in  the  manner 
stated.  Should  the  lever  of  the  regulator  remain  down,  it  shows 
that  the  speed  of  the  machine  is  not  sufficient  to  supply  the  cir- 
cuit, or  that  the  machine  is  overloaded  with  lights. 

The  controller  magnet  should  be  constantly  opening  and 
closing  its  contacts.  This  movement  is  very  slight.  The  arc  of 
the  2000  c.  p.  lamps  should  be  -f^"  to  1"  in  length  and  the  1200 
c.  p.  lamps  should  have  an  arc  -fa"  to  11B"  in  length.  If  the  car- 
bons are  of  good  quality,  the  arc  should  not  flame  or  hiss. 

INSTRUCTIONS    FOR   REPAIRING,  TESTING  AND  ADJUSTING 

ARC  LIGHTS. 

It  frequently  becomes  necessary,  after  the  lamps  have  been  in 
use  for  a  considerable  length  of  time,  to  repair  and  readjust  them. 

After  cleaning  and  repairing,  the  lamp  should  be  tested  and 
readjusted.  Experience  shows  that  whenever  even  one  new  part 
has  been  put  into  a  lamp  or  generator,  trouble  may  result  if  tests 
and  readjustments  are  not  made  before  putting  the  apparatus  into 
regular  service. 

In  order  to  properly  test  the  lamps  that  have  been  repaired, 
select  some  part  of  the  engine  room  where  the  lamps  can  be  hung 


154  HANDBOOK    ON    ENGINEERING. 

up  and  burned  without  being  subjected  to  drafts  of  air ;  other- 
wise, they  may  hiss  and  act  badly,  no  matter  how  carefully  the 
adjustments  may  be  made. 

When  the  lamps  have  been  hung  up  and  attached  to  the 
hanger  boards,  or  some  similar  arrangement  for  connecting  to  the 
circuit  in  the  usual  manner,  the  carbon  rods  should  be  cleaned 
thoroughly  with  cotton  waste.  If  any  sticky  or  dirty  spots 
appear,  which  cannot  be  readily  removed  with  waste,  use  a  piece 
of  well-worn  crocus  cloth,  always  being  careful  to  use  a  piece  of 
clean  waste  before  pushing  the  rod  up  into  the  lamp.  Under  no 
circumstances  whatever  should  the  rods  be  pushed  up  into  the 
lamps  in  a  dirty  condition  ;  they  should  always  be  cleaned  in  the 
manner  described. 

The  tension  of  the  clamp  which  holds  the  rod  is  adjusted  by 
raising  or  lowering  the  arm  at  the  top  of  the  guide  rod.  If  the 
tension  is  too  great,  the  rod  and  clutch  will  wear  badly  and  the 
feeding  will  be  uneven,  causing  unsteadiness  in  the  lights.  Too 
light  tension  will  not  allow  the  clutch  to  hold  up  the  rod  and  any 
sudden  jar  to  the  lamp  will  cause  the  rod  to  fall  and  the  light  to 
go  out. 

The  double  carbon  or  M  lamp  should  have  the  tension  of  the 
second  carbon  rod  a  trifle  lighter  than  the  first  one. 

When  adjusting  the  tension,  be  sure  to  keep  the  guide  rod 
perpendicular  and  in  perfect  line  with  the  carbon  rod  ;  jt  should 
be  free  to  move  up  and  down  without  sticking. 

The  tension  of  the  clutch  in  the  D  lamp  should  be  the  same  as 
that  of  the  K  lamp.  It  is  adjusted  by  tightening  or  loosening 
the  small  coil  spring  from  the  arm  of  the  clutch  to  the  bottom  of 
the  clamp  stop. 

To  adjust  the  feeding  point  in  the  K  lamp,  press  down  the 
main  armature  as  far  as  it  will  go,  then  push  up  the  rod  about 
one-half  its  length,  let  go  the  armature  and  then  press  it  down 
slowly,  and  note  the  distance  of  the  bottom  side  of  the  armature 


HANDBOOK    ON    ENGINEERING.  155 

above  the  base  of  the  curved  part  of  the  pole.  When  the  rod 
just  feeds,  this  distance  should  be  J".  If  it  is  not,  raise  or  lower 
the  small  stop  which  slides  on  the  guide  rod  passing  through  the 
arm  of  the  clutch,  until  the  carbon  rod  will  feed  when  the  arma- 
ture is  |"  from  rocker  frame  at  the  base  of  the  pole. 

To  adjust  the  feeding  point  of  the  M  lamp,  adjust  the  first  rod 
as  in  the  K  lamp.  Then  let  the  first  rod  down  till  the  cap  at  the 
top  rests  on  the  transfer  lever.  The  second  rod  should  feed  with 
the  armature  at  a  point  y1^"  higher  than  it  was  while  feeding  the 
first  rod,  that  is,  it  should  be  T\"  from  rocker  frame  at  base  of 
pole. 

The  feeding  point  of  the  D  lamp  is  adjusted  by  sliding  the 
clamp  stop  up  or  down,  so  that  the  rod  will  feed,  when  the  rela- 
tive distances  of  the  armature  of  the  lifting  magnet  and  the 
armature  of  the  shunt  magnet  from  rocker  frame  are  in  the  ratio 
of  1  to  2.  There  should  be  a  slight  lateral  play  in  the  rocker, 
between  the  lugs  of  the  rocker  frame. 

M*ake  a  careful  examination  of  all  joints,  screws,  wires  and 
other  parts  of  the  lamps.  The  armatures  of  all  the  magnets  should 
be  central  with  cores,  and  come  down  squarely  and  evenly.  There 
should  be  a  separation  of  -fa"  between  the  silver  contact  points, 
when  the  armature  of  the  starting  magnet  is  down.  This  contact 
should  be  perfect  when  the  armature  is  up.  The  arm  for 
adjusting  the  tension  should  not  touch  the  wire  or  frame  of  the 
lamp,  when  at  the  highest  point.  There  should  be  a  space  of 
^2"  or  i"  between  the  body  of  the  clutch  and  the  arm  of  the 
clutch,  to  allow  for  wear  on  the  bearing  surfaces. 

Always  trim  the  lamps  with  carbons  of  proper  length  to  cut 
out  automatically,  that  is,  have  twice  as  much  carbon  projecting 
from  the  top  as  from  the  bottom  holder.  Always  allow  a  space 
of  J"  when  the  lamp  is  trimmed,  from  the  round  head  screw  in 
the  rod,  near  the  carbon  holder,  to  the  edge  of  upper  bushing,  so 
that  there  will  be  sufficient  space  to  start  the  arc.  Be  careful  to 


156  HANDBOOK    ON    ENGINEERING. 

get  the  carbons  as  accurately  centered  as  possible.  They  will 
generally  come  right  after  one  or  two  trials. 

The  arcs  of  the  1200  candle-power  lamps  should  be  adjusted 
t°A"»  with  full  length  of  carbon.  Arcs  of  2000  candle-power 
lamps  should  be  adjusted  from  -I1^"  to  33.,"  when  good  carbons  are 
used.  Lamps  should  always  maintain  a  fairly  even  arc.  The 
length  of  the  arc  will  slightly  increase  as  the  carbons  burn  away, 
but  they  should  not  hiss,  flame,  or  overfeed  at  any  time.  If  the 
switch  is  thrown  and  the  lamp  cutoff,  and  then  turned  on  quickly, 
the  upper  carbon  should  "  pick  up  "  promptty  with  a  normal  arc, 
not  hiss  over  a  few  seconds,  and  then  burn  as  quietly  as  before. 

When  the  upper  carbon  rod  is  drawn  up  by  the  hand,  the 
lamp  should  cut.  out  promptly  and  not  "  flash"  the  generator. 
In  the  case  the  arc  is  very  long  or  causes  flashing,  look  at  the 
contacts  and  see  that  they  are  clean  and  make  a  good  square  con- 
tact. Also  examine  the  centering  of  the  armature.  The  cause 
of  the  trouble  will  usually  be  found  in  one  of  these  places. 

The  action  of  a  lamp  that  feeds  badly  may  often  be  con- 
founded with  that  of  a  badly  flaming  carbon.  The  distinction 
can  readily  be  made  after  a  short  observation.  The  arc  of  a  lamp 
that  feeds  badly  will  gradually  grow  long  until  it  flames,  the 
clutch  will  let  go  suddenly,  the  upper  carbon  will  fall  until  it 
touches  the  lower  carbon,  and  then  pick  up.  A  bad  carbon  may 
burn  nicely  and  feed  evenly,  until  a  bad  spot  in  the  carbon  is 
reached,  when  the  arc  will  suddenly  become  long  and  flame  and 
smoke,  due  to  impurities  in  the  carbon.  Instead  of  dropping  as 
in  the  former  case,  the  upper  carbon  will  feed  to  its  correct  posi- 
tion, without  touching  the  lower  carbon. 

After  the  lamp  has  been  tested  and  burns  satisfactorily  in  the 
station,  tighten  up  the  adjusting  screws,  and  if  necessary,  put  a 
small  amount  of  thick  shellac  on  the  bottom  of  the  guide  rod. 
This  will  prevent  the  stop  from  falling,  in  case  the  screw  which 
holds  it  becomes  loose  or  broken.  The  lamps  are  now  ready  to 


HANDBOOK    ON    ENGINEERING.  157 

be  placed  on  the  circuit,  but  if  it  is  necessary  to  store  them,  they 
should  be  put  into  some  part  of  the  building  or  engine  room  where 
they  will  not  become  covered  with  dust  before  they  are  taken  out. 
If  they  become  dusty,  use  a  small  hand  bellows  to  blow  away  the 
dust  which  may  have  collected  on  the  working  parts  of  the  lamps, 
before  placing  them  on  the  circuit. 

SUMflARY. 

Xhs  following'  summary  of  the  foregoing  instructions  may  be 
Useful  for  the  guidance  of  men  in  charge  of  dynamos :  — 

1.  In  operating  an  arc  system,  attend  strictly  to  all  the  points 
herein  given. 

2.  Be  sure  that  the  speed  of  the  dynamo  is  right  and  that  the 
belt  has  its  proper  tension. 

3.  See  that  the  regulator  always  works  properly,  arid  has  suffi- 
cient "  surplus  "  or  space  between  its  armature  and  the  stop. 

4.  lie  careful  that  all  connections  of  wires  are  well  made. 

5.  Do  not  allow  the  circuit  to  become  uninsulated  at  any  point. 

6.  Keep   every  part  of  the  machine    and  lamps    scrupulously 
clean . 

7.  Keep  all    the  insulations    free  from   metallic  dust  or  gritty 
substances,  by  a  careful  cleaning  once  a  day. 

8.  Keep   the    bearings  of  the  machine  well  supplied  with  the 
best  quality  of  mineral  oil. 

9.  Do   not  use  water  or  ice  on  a  bearing  in  case  of  heating,  as 
the  water  is  liable  to  get  into  the  armature  and  injure  the  insula- 
tion. 

10.  Lubricate    the  commutator  of    the   C  and  E  machines  b^ 
touching  the  surface  occasionally  with  an  oiled  cloth. 

11.  The  commutator   on    the  machine  is  set  carefully  before 
leaving  the  factory  in  the    best  position  for  proper  working,  and 
its  position  marked  by  chisel  marks  on  the  commutator  and  shaft, 


158  HANDBOOK    ON    ENGINEERING. 

If  the  commutator  is  ever  removed  from  the  machine,  it  must  be 
put  back  in  exactly  the  same  position  on  the  shaft,  and  the  red, 
white  and  blue  leads  must  be  put  into  the  posts  marked  1,  2  and 
3  respectively.  If  wrongly  placed,  the  machine  will  either  not 
generate,  or  will  act  very  badly. 

12.  When  the  commutator  segments  become  badly  worn,  they 
may  be  turned  down  in  a  lathe,  either  by  removing  the  commu- 
tator entirely  from  the  shaft  of  the  machine  and  putting  it  upon 
an  arbor,  or  by  removing  the  segments  separately  and  screwing 
them  to  a  jig,  which  may  then  be  put  into  the  lathe.     The  use  of 
the  jig  is  especially  recommended  for  turning  down  the  segments 
as  the  adjustment  of   the  commutator  is  less  liable  to  be  changed 
than  when  the  arbor  is  used. 

13.  The  durability  of  the  commutator  segments  will  depend  on 
the  care  exercised  in  the  running  of  the  machine. 

14.  The  brushes   must  be    set    carefully  by  the    "gauge   for 
brushes,"  in  the  manner  explained  before. 

15.  The  spark  on  the  tips  of  the  brushes  will  vary  with  the  set 
and  wear  of  the  brushes.     It  should  be  from  1"  to  J"  long,  and 
only  on  the  forward  brushes. 

16.  The  carbon  rods  in  every  lamp  should  be  carefully  cleaned 
daily. 

17.  The    carbons    should    be  in  perfect  alignment  and  firmly 
clamped  in  the  holders. 

18.  If  a  lamp  burns  badly  and  with  a  bluish  flame,  or  contin- 
ually hisses,  it  is  probably  due  to  poor  carbons,  which  should  be 
removed  and  better  ones  substituted. 

19.  The  lamps  rarely  burn  as  well  when  first  started  as  after- 
wards.    This   is  principally  due    to   the  fact  that  the    carbons 
require  a  little  time  to  burn  to  the  proper  shape. 

20.  The  automatic  regulator  prevents  the  machine  from  gener- 
ating more  than  the  amount  of  current  required,  so  that  the  lamps 
may  be  thrown  on  or  off  the  circuit  at  pleasure. 


HANDBOOK    ON   ENGINEERING. 


159 


21.  Do  not  tamper  with  adjustments  made  in  the  factory. 

22.  Do  not  imagine  that  every  time  a  lamp  hisses  or  flames  a 
little  it  is  out  of  adjustment.     As  a  rule,  bad  working  is  due  to 
stickiness  of  the  moving  parts,  or  to  poor  carbons.     The  lamps 
once  properly  adjusted  and  operated  with  good  carbons,  should 
not  get  out  of  adjustment,  and  should  be  let  alone  in  that  respect. 

23.  If  the  machine  works  badly,  it  should  be  tested  with  a  mag- 
neto for  grounds  of  connection  between  the  circuit  and  the  frame 
of  the  machine.     The  circuit  should  also  be  daily  tested,  and  any 
faults  found  should  be  immediately  remedied,  as  otherwise  they 
will  inevitably  cause  trouble. 

24.  All  construction  and  repair  work  should  be  done  in  strict 
accordance  with  the  rules  herein  laid  down. 

TABLE    OF     MAGNETIZING    FORCE     IN    AMPEKE    TURNS    REQUIRED    PEK 
INCH  OF    LENGTH  OF    MAGNETIC  CIRCUIT. 


Magnetic  Den- 
sity per  square 
inch  in 
Gausses. 

MAGNETIZING  FORCE  IN  AMPERE  TURNS. 

Air. 

Cast  Iron. 

Steel. 

Wrought  Iron. 

5,000 

1,567 

3.80 

2.85 

1.50 

10,000 

3,134 

5.35 

4.25 

2.40 

15,000 

4,701 

6.80 

5.35 

3.20 

20,000 

6,268 

8.00 

6.30 

3.90 

25,000 

7,835 

10.30 

7.50 

4.60 

30,000 

9,402 

16.20 

8.80 

5.30 

35,000 

10,969 

28.70 

10.20 

5.90 

40,000 

12,536 

49.00 

11.70 

6.50 

45,000 

14,103 

80.00 

13.40 

7.10 

50,000 

15,670 

160.00 

15.40 

8.20 

55,000 

17,237 

240.00 

17.80 

9.50 

60,000 

18,804 

350.00 

20.70 

11.00 

65,000 

20,371 

490.00 

24.10 

13.50 

70,000 

21,938 

650.00 

28.00 

17.00 

75,000 

23,505 

34.00 

21.80 

80.000 

25.072 

42.00 

27.50 

160  HANDBOOK    OX     KXCJIXKKKING. 


CHAPTER     Xa. 

Incandescent  Wiring  Table. 

Table  on  two  following  pages  is  arranged  to  enable  wiremen  to 
select  the  right  sizes  of  wire  for  service  connections  and  inside 
work.  The  figures  at  the  top  indicate  distance  in  feet  to  center 
of  distribution,  in  reality  half  the  length  of  the  circuit ;  the  four 
columns  at  the  left  showing  the  number  of  16-candle  power  lamps 
at  various  voltages  ;  the  other  figures  showing  the  sizes  of  wire, 
Brown  &  Sharpe  gauge,  to  be  used  for  distributing  the  number  of 
lamps  stated  at  the  distances  indicated  and  with  the  loss  of  1 
volt. 

For  example:  To  distribute  30  lamps  of  110  volts  at  a  dis- 
tance of  80  feet  with  a  loss  of  1  volt.  In  column  of  110-volt 
lamps  find  the  number  30,  then  follow  the  same  line  of  figures  to 
the  right  until  the  column  headed  80  is  reached,  and  it  appears 
that  No.  6  wire  must  be  used. 

The  same  table  may  be  used  for  other  losses  than  1  volt  by 
dividing  the  given  number  of  lamps  by  the  number  of  volts  to  be 
lost,  then  with  this  product  proceed  as  before  in  the  table. 

For  example :  To  distribute  30  lamps  of  110  volts  at  a  distance 
of  80  feet  with  a  loss  of  2  volts,  divide  30  by  2  which  gives  15, 
then  find  15  in  the  column  headed  110  volts  and  follow  the  same 
line  of  figures  to  the  right  until  column  headed  80  is  reached,  and 
it  is  found  -that  No.  8  wire  must  be  used. 

No  wire  smaller  than  No.  14  is  shown  in  the  table  as  the  Na- 
tional Board  of  Fire  Underwriters  prohibits  the  use  of  a  smaller 
size.  Odd  sizes  smaller  than  No.  5  are  not  commercial  and  are 
therefore  omitted. 


HANDBOOK    OX    ENGINEERING. 


161 


Incandescent  Wiring  Table. 

Sixteen  Candle  Power  Lamps.  Loss,  One  Volt. 

TABLE  No.  1.          Sizes  of  Wire  are  by  B.  &  S.  Gauge. 


52  Volt 
8i 

110  Volt 

*! 

220  Volt 
4 

550  Volt 
4 

Distance  in  feet  to  center 
of  Distribution. 

Watt 

Watb 

Watt 

Watt 

Lamps 

Lamps 

Lamps 

Lamps 

20' 

25' 

30' 

87 

40' 

45' 

1 

2 

3 

9 

14 

14 

14 

14 

14 

14 

2 

4 

7  ' 

18 

14 

14 

14 

14 

14 

14 

3 

6 

11 

28 

14 

14 

14 

14 

14 

14 

4 

8 

15 

37 

14 

14 

14 

14 

14 

14 

5 

10 

18 

46 

14 

14 

14 

14 

12 

12 

6 

12 

22 

56 

14 

14 

14 

12 

12 

12 

7 

15 

26 

65 

14 

14 

12 

12 

12 

10 

8 

17 

30 

74 

14 

12 

12 

12 

10 

10 

9 

19 

33 

83 

14 

12 

12 

10 

10 

10 

10 

21 

37 

93 

12 

12 

12 

10 

10 

10 

12 

25 

44 

111 

12 

10 

10 

10 

8 

8 

14 

30 

52 

130 

12 

10 

10 

8 

8 

8 

16 

34 

59 

148 

10 

10 

8 

8 

8 

8 

18 

38 

66 

167 

10 

8 

8 

8 

8 

6 

20 

42 

74 

185 

10 

8 

8 

8 

6 

6 

25 

53 

92 

232 

8 

8 

6 

6 

6 

6 

30 

63 

111 

278 

8 

6 

6 

6 

5 

5 

35 

74 

130 

324 

6 

6 

6 

5 

5 

4 

40 

85 

148 

371 

6 

6 

6 

5 

4 

4 

45 

95 

166 

428 

5 

5 

5 

4 

4 

3 

50 

106 

186 

464 

5 

5 

4 

4 

3 

3 

55 

116 

203 

510 

4 

4 

4 

3 

3 

2 

60 

127 

222 

557 

4 

4 

4 

3 

2 

2 

G5 

138 

240 

603 

3 

3 

3 

3 

2 

2 

70 

148 

260 

650 

3 

3 

3 

2 

2 

1 

75 

159 

277 

696 

2 

2 

2 

2 

1 

1 

80 

170 

296 

742 

2 

2 

2 

2 

1 

1 

90 

191 

333 

835 

1 

1 

1 

l 

1 

0 

100 

212 

370 

928 

1 

1 

1 

1 

0 

0 

162 


HANDBOOK    ON    ENGINEERING. 


Incandescent  Wiring  Table. 

Sixteen  Candle  Power  Lamps,  Loss,  One  Volt. 
TABLE  No.  1.          Sizes  of  Wire  are  by  B.  &  S.  Gauge. 


DISTANCE   IN    FEET    TO    CENTER   OF    DISTRIBUTION. 


50' 

60' 

70' 

80' 

90' 

100' 

120' 

140' 

160' 

180' 

200' 

14 

14 

14 

14 

14 

14 

14 

14 

14 

14 

12 

14 

14 

14 

14 

14 

12 

12 

12 

10 

10 

10 

14 

14 

12 

12 

12 

10 

10 

10 

8 

8 

8 

12 

12 

12 

10 

10 

10 

8 

8 

8 

8 

6 

12 

10 

10 

10 

10 

8 

8 

8 

6 

6 

6 

10 

10 

10 

8 

8 

8 

8 

6 

6 

6 

6 

10 

10 

8 

8 

8 

8 

6 

6 

6 

5 

5 

10 

8 

8 

8 

8 

6 

6 

6 

5 

5 

4 

10 

8 

8 

8 

6 

6 

6 

5 

5 

4 

4 

8 

8 

8 

6- 

6 

6 

5 

5 

4 

4 

3 

8 

8 

6 

6 

6 

5 

5 

4 

3 

3 

2 

8 

6 

6 

6 

5 

5 

4 

3 

3 

2 

2 

6 

6 

6 

5 

5 

4 

3 

3 

2 

2 

1 

6 

6 

5 

5 

4 

4 

3 

2 

2 

1 

1 

6 

5 

5 

4 

4 

3 

2 

2 

1 

1 

0 

5 

5 

4 

3 

3 

2 

1 

1 

0 

0 

00 

5 

4 

3 

2 

2 

1 

1 

0 

0 

00 

00 

4 

3 

2 

2 

1 

1 

0 

00 

00 

000 

000 

3 

2 

2 

1 

1 

0 

00 

00 

000 

000 

0000 

3 

2 

1 

1 

0 

0 

00 

000 

000 

0000 

0000 

2 

1 

1 

0 

0 

00 

000 

000 

0000 

0000 

2 

1 

0 

0 

00 

00 

000 

0000 

0000 

1 

1 

0 

00 

00 

000 

000 

0000 

0000 

1 

0 

0 

00 

00 

000 

0000 

0000 

1 

0 

00 

00 

000 

000 

0000 

0 

0 

00 

000 

000 

0000 

0000 

0 

00 

00 

000 

000 

0000 

0 

00 

000 

000 

0000 

0000 

00 

000 

000 

0000 

0000 

HANDBOOK    ON    ENGINEERING, 


163 


Feet  x  2  x  10.70. 


TABLE  No.  2. 


Feet 
to  end  of 
Circuit. 

Ft.  x2x!0.70. 

Feet 
to  end  of 
Circuit. 

Ft.  x2x!0.70. 

Feet 
to  end  of 
Circuit. 

Ft.x2xlO.70. 

5 

107 

185 

3,959 

365 

7,811 

10 

214 

190 

4,066 

370 

7,918 

15 

321 

195 

4,173 

375 

8,025 

20 

428 

200 

4,280 

380 

8,132 

25 

535 

205 

4,387 

385 

8,239 

30 

642 

210 

4,494 

390 

8,346 

35 

749 

215 

4,601 

395 

8,453 

40 

856 

220 

4,708 

400 

8,560 

45 

963 

225 

4,815 

405 

8,667 

50 

,070 

230 

4,922 

410 

8,774 

55 

,177 

235 

5,029 

415 

8,881 

60 

,284 

240 

5,136 

420 

8,988 

65 

,391 

245 

5,243 

425 

9,095 

70 

,498 

250 

5,350 

430 

9,202 

75 

,605 

255 

5,457 

435 

9,309 

80 

,712 

260 

5,564 

440 

9,416 

85 

,819 

265 

5,671 

445 

9,523 

90 

,926 

270 

5,778 

450 

9,630 

95 

2,033 

275 

5,885 

455 

9,737 

100 

2,140 

280 

5,992 

460 

9,844 

105 

2,247 

285 

6,099 

465 

9,951 

110 

2,354 

290 

6,206 

470 

10,058 

115 

2,461 

295 

6,313 

475 

10,165 

120 

2,568 

300 

6,420 

480 

10,272 

125 

2,675 

305 

6,527 

485 

10,379 

130 

2,782 

310 

6,634 

490 

10,486 

135 

2,889 

315 

6,741 

495 

10,593 

140 

2,996 

320 

6,848 

500 

10,700 

145 

3,103 

325 

6,955 

510 

10,914 

150- 

3,210 

330 

7,062 

520 

11,128 

155 

3,317 

335 

7,169 

530 

11,342 

160 

3,424 

340 

7,276 

540 

11,556 

165 

3,531 

345 

7,383 

550 

11,770 

170 

3,638 

350 

7,490 

560 

11,984 

175 

3,745 

355 

7,597 

570 

12,198 

180 

3,852 

360 

7,704 

580 

12,412 

164 


HANDBOOK   ON   ENGINEERING. 


Feetx2xl0.70. 


TABLE  No.  2. 


Feet 
to  end  of 
Circuit. 

Ft.x2xlO.70. 

Feet 
to  end  of 
Circuit. 

Ft.x2xlO.70 

Feet 
to  end  of 
Circuit. 

Ft.x2xlO.70. 

590 

12,626 

970 

20,758 

1,350 

28,890 

600 

12,840 

980 

20,1)72 

1,360 

29,104 

610 

13,054 

900 

21,186 

1,370 

29,318 

620 

13,268 

1,000 

21,400 

1  ,380 

29,532 

630 

13,482 

1,010 

21,614 

1,390 

29,746 

640 

13,696 

1,020 

21,828 

1,400 

29,960 

650 

13,910 

1,030 

22,042 

1,410 

30,174 

660 

14,124 

1,040 

22,256 

1,420 

30,388 

670 

14,338 

1,050 

22,470 

1,430 

30,602 

68.0 

14,552 

1,060 

22,684 

1,440 

30,816 

690 

14,766 

1,070 

22,898 

1,450 

31,030 

700 

14,980 

1,080 

23,112 

1,460 

31,244 

710 

15,194 

1,090 

23,326 

1,470 

31,458 

720 

15,408 

1,100 

23,540 

1,480 

31,672 

730 

15,622 

1,110 

23,764 

1,490 

31,886 

740 

15,836 

1,120 

23,968 

1,500 

32,100 

750 

16,050 

1,130 

24,182 

1,510 

32,314 

760 

16,264 

1,140 

24,396 

1,520 

32,528 

770 

16,478 

1,150 

24,610 

1,530 

32,742 

780 

16,692 

1,160 

24,824 

1,540 

32,956 

790 

16,906 

1,170 

25,038 

1,550 

33,170 

800 

17,120 

1,180 

25,252 

1,5(50 

33,3«4 

810 

17,334 

1,190 

25,466 

1,570 

33,598 

820 

17,548 

1,200 

25,680 

1,580 

33,812 

830 

17,762 

1,210 

25,894 

1,590 

34,026 

840 

17,976 

1,220 

26,108 

1,600 

34,240 

850 

18,190 

1,230 

26,322 

1,610 

34,454 

860 

18,404 

1,240 

26,536 

1,620 

34,668 

870 

18,618 

1,250 

26,750 

1,630 

34,882 

880 

18,832 

1,260 

26,964 

1,640 

85,096 

890 

19,046 

1,270 

27,178 

1,650 

35,310 

900 

19,260 

1,280 

27,392 

1,660 

35,524 

910 

19,474 

1,290 

27,606 

1,670 

35,738 

920 

19,688 

1,300 

27,820 

1,680 

35,952 

930 

19,902 

1,310 

28,034 

1,690 

36,166 

940 

20,116 

1,320 

28,248 

1,700 

36,380 

950 

20,330 

1.330 

28,462 

1,710 

36,594 

9GO 

20,544 

1,340 

28,676 

1,720 

36,808 

HANDBOOK   ON   ENGINEERING. 


165 


Feetx  2x10.70. 


TABLE  No.  2. 


Feet 

Feet 

Feet 

to  end  of 

Ft.x2xlO.70. 

to  end  of 

Ft.x2xlO.70. 

to  end  of 

Ft.x2xlO.70. 

Circuit. 

Circuit. 

Circuit. 

1,730 

37,022 

2,450 

52,430 

4,250 

90,950 

1,740 

37,230 

2,500 

53,500 

4,300 

92,020 

,750 

37,450 

2,550 

54,570 

4  350 

93.090 

,760 

37,064 

2,000 

55,640 

4,400 

94,100 

,770 

37,878 

2,050 

50,710 

4,450 

95,230 

,780 

38,092 

2,700 

57,780 

4,500 

96300 

,71)0 

38,306 

2,750 

58,850 

4,550 

97,370 

,800 

38,520 

2,800 

59,920 

4,000 

98,440 

,810 

38,734 

2,850 

60,990 

4,050 

99,510 

,820 

38,948 

2,900 

62,000 

4,700 

100,580 

,830 

39,102 

2,950 

63,130 

4,750 

101,650 

,840 

39,376 

3,000 

64,200 

4,800 

102,720 

,850 

39  590 

3,050 

65,270 

4,850 

103,790 

,800 

39,804 

3,100 

66,340 

4,900 

104,860 

,870 

40  018 

3,150 

67,410 

4,950 

105>930 

,880 

40,232 

3,200 

68,480 

5,000 

107,000 

,890 

40,446 

3,250 

69,550 

5,050 

108,070 

,900 

40,060 

3,300 

70,620 

5,100 

109,140 

,910 

40,874 

3,350 

71,090 

5,150 

110,210 

,920 

41,088 

3,400- 

72,760 

5,200 

111,280 

,930 

41,302 

3,450 

73,830 

5,250 

112,350 

,940 

41,516 

3,500 

74,900 

5,300 

113,420 

,1)50 

41,730 

3,550 

75,970 

5,350 

114,400 

,960 

41,944 

3,600 

77,040 

5,400 

115,560 

,970 

42,158 

3,650 

78,110 

5,450 

116,630 

,980 

42,372 

3,700 

79,180 

5,500 

117,700 

,990 

42,586 

3,750 

80,250 

5,550 

118,770 

2,000 

42,800 

3,800 

81  320 

5,000 

119,840 

2,050 

43,870 

3,850 

82,390 

5,050 

120,910 

2,100 

44,940 

3,900 

83,460 

5,700 

121,980 

2,150 

46,010 

3.950 

84,530 

5,750 

123,050 

2/200 

47,080 

4,000 

85,600 

5,800 

"  124,120 

2,250 

48,150 

4,050 

86,670 

5,850 

125,190 

2,300 

49,220 

4,100 

87,740 

5,900 

126,260 

2,350 

"  50,290 

4,150 

88,810 

5,950 

127,330 

2,400 

51,300 

4,200 

89,880 

6,000 

128,400 

166 


TABLE  No.  2. 


HANDBOOK    ON    ENGINEERING, 

Feet  x  a  x  10.70. 


Miles. 

Ft.x2xlO.70 

Miles. 

Ft.x2xlO.70 

Miles. 

Ft.x2xlO.70 

i 

564,960 

4 

451,968 

n 

847,440 

112,992 

4i 

508,464 

8 

903,936 

i& 

169,488 

5 

564,960 

M 

960,432 

2 

2*25,984 

Si 

621,456 

9 

1,016,928 

2i 

282,480 

6 

677,952 

0* 

1,073,424 

3 

338,976 

6* 

734,448 

10 

1,129,920 

« 

395,472 

7  • 

.790,944 

(A) 


Feet  x  2  x  10.7  x  Amperes 


=  Circular  nails. 


Volts  lost 

Feetx  2x  10.7  x  Amperes      Tr  .     . 

(B)  ^ -. .-  -=Volts  lost. 

^  *  •  .'iVSftll  lai*      TVI1   I  C3 


(C) 


Circular  mils. 
Circular  mills  x  volts  lost 


=  Amperes. 


Feetx  2  x  10.7 

In  calculating  the  sizes  of  wire  as  shown  in  the  Incandescent 
Wiring  Table  a  formula  (A)  has  been  used  in  which  there  is  a 
constant  10.7,  the  number  of  circular  mils  in  a  copper  wire  which 
would  have  a  resistance  of  one  ohm  for  one  foot  of  length.  One 
ampere  through  one  ohm  resistance  loses  one  volt.  To  determine 
the  size  of  wire  necessary  for  carrying  a  given  current  a  given 
distance  in  feet,  multiply  the  number  of  feet  by  2  to  obtain  the 
actual  length  of  circuit,  multiply  this  product  by  the  constant 
10.7  and  it  will  give  the  circular  mils  necessary  for  one  ohm  re- 
sistance, multiply  this  by  the  amperes  and  it  gives  the  circular 
mils  necessary  for  the  loss  of  one  volt.  Divide  this  last  result 
by  the  volts  lost  and  it  gives  the  circular  mils  necessary.  Hence 
the  formula  "A." 

By  simply  transposing  the  terms  we  obtain  formula  "  B,"  which 
can  be  ueed  to  determine  the  volts  lost  in  a  given  length  of  wire 
of  certain  size  carrying  a  certain  number  of  amperes. 


HANDBOOK    ON    ENGINEERING.  167 

Again,  by  another  change  in  the  terms,  we  obtain  formula 
"  C,"  which  shows  the  number  of  amperes  which  a  wire  of  given 
size  and  length  will  carry  at  a  given  number  of  volts  lost. 

Table  No.  2  has  been  arranged  for  the  purpose  of  saving  time 
in  the  use  of  these  formulae.  It  shows  the  result  of  Feet  x  2  x 
10.7  for  various  distances  over  which  it  may  be  desired  to  trans- 
mit current. 

A  few  examples  will  assist  in  showing  the  use  of  the  formulas 
and  tables. 

Suppose  we  wish  to  distribute  300  16  c.  p.  3.5  watt  lamps  of 
110  volts  at  a  distance  of  490  feet  with  a  loss  of  10  per  cent. 
Using  formula  A, 

490  feet  x  2  x  10.7  (find  it  in  table  No.  2)  =  10486. 
300  lamps  of  110  volts  =  152.7  amperes. 
(See  table  No.  3  for  amperes  per  lamp,  and  multiply  by  300.) 
10  per  cent  loss  on    110  volt  system  =  12.22  volts.     (See 

table  No.  4.) 
10486  x  152.7  amperes  =  1601212  circ.  mite.  ^  12.22  volts 

lost—  131032  circ.  mils. 

In  our  table  it  shows  the  size  of  wire  for  this  number  of  circ. 
mils,  to  be  00. 

To  check  this  and  determine  exactly  the  volts  lost  in  this  cir- 
cuit by  using  No.  00  wire,  use  formula  B,  as  follows: 

10,486  x  152.7  amperes  =  1601212 ~-  133079  circ.  mils.  = 
12.03  volts  lost. 

Suppose  it  is  desired  to  distribute  1,000  lamps  at  a  distance  of 
1950  feet  by  3-wire  system,  viz.,  220  volts,  with  a  loss  of  10  per 
cent. 

Using  formula  A, 

1950  feet  x  2  x  10.7  (see  table)  =  41730. 
1000  lamps  on  220  volt  system  =  291  amperes. 
(See  table  No.  5  for   amperes   per  lamp,  and   multiply   by 
1000.) 


168  HANDBOOK    ON    ENGINEERING. 

10   per  cent  on  220  volt  system  =  24. 44  volts  lost.     (See 

table  No.  4.) 
41730    x    291     amperes  =  12143430-:- 24.44     volts     lost 

=  496867  circ.  mils. 
500000  circ.  mils,   the  nearest  commercial  size,   should  be 

used. 
,   Check  this  as  before  by  formula  B. 

41730   x   291    amperes  =  12 143430 -^-500000     circ.      mils 

=  24.29  volts  lost. 

Suppose   we  wish  to  deliver    100  h.  p.  to  a  500  volt  motor,  at 
a  distance  of  4850  feet  with  10  per  cent  loss : 
Again  using  formula  A, 

4850  feet  x  2  x  10.7  =  103790. 

100  h.  p.  at  500  volts  =  160  amperes.     (See  table  No.  3.) 

10   per  cent  loss  on   500  volts  system  =  55. 5  volts.      (See 

table  No.  4.) 
103790  x  160. amperes  =  16606400 -j- 55.5    volts  =  299215 

circ.  mils. 

300000  circ.  mils,  cable  should  be  used. 
Check  this  as  before  by  formula  B. 

103790    x    160    amperes  =  16606400  -*-  300000    circ.    mils 

=  55.35  volts  lost. 

To  ascertain  how  many  amperes  could  be  carried  to  a  distance 
of  4850  feet  with  500  volts  with  10  per  cent  loss,  use  formula  C  : 
4850  feet  x  2  x  10.7  =  103790. 
10  per  cent  loss  on  500  volts  system  =  55.5  volts. 
300000  circ.  mils  x  55.5  volts  lost -~- 103790  =  160.42  am- 
peres, which  as  will  appear  by  reference   to  table  No.  3, 
will  permit  the  use  of  100  h.  p.  motor. 


HANDBOOK   ON   ENGINEERING. 


169 


Amperes  per  Motor, 


TABLE  No.  8. 


H.  P. 

Per  Cent 
Efficiency 

Watts. 

VOLTS. 

110 

115 

120 

1 

65 

860 

7.82 

7.48 

7.17 

65 

1148 

10.4 

9.98 

9.57 

2 

65 

2295 

20.8 

200 

19.1 

24 

75 

2487 

22  6 

21.6 

20.7 

$4 

75 

3480 

31.6 

30.3 

29.0 

5 

80 

4662 

42  4 

40.5 

388 

ft 

80 

6994 

63  6 

60.8 

58.3 

10 

85 

8776 

79.8 

76.3 

73.1 

15 

85 

13165 

120. 

114. 

110. 

20 

90 

16578 

151. 

144. 

138. 

25 

90 

20722 

188. 

180.. 

173. 

30 

90 

24867 

2^6. 

216. 

207. 

40 

90 

33155 

301. 

288. 

276. 

50 

90 

41444 

377. 

360. 

345. 

70 

90 

58022 

528. 

505. 

484. 

90 

90 

74600 

678. 

649. 

622. 

100 

93 

80215 

729. 

697. 

668. 

125 

93 

100269 

912. 

872. 

836. 

150 

93 

120323 

1094. 

1046. 

1003. 

The  above  table  is  arranged  to  show  the  amperes  per  motor  at  dif- 
ferent voltages  for  several  sizes  of  motors  at  efficiencies  obtained  in 
ordinary  practice. 


170 


HANDBOOK   ON   ENGINEERING. 


Amperes  per  Motor. 


TABLE  No.  8. 


VOLTS. 


125 

220 

250 

500 

525 

550 

6.88 

3.91 

3.44 

1.72 

1.64 

1.56 

9.18 

5.22 

4.59 

2.30 

2.19 

2.09 

18.4 

10.4 

9.18 

4.59 

4.37 

4.17 

19.9 

11.3 

9.95 

4.97 

4.74 

4.52 

27.8 

16.8 

13.9 

6.96 

6.63 

6.33 

37.3 

21.2 

18.6 

9.32 

8.88 

8.48 

56.0 

31.8 

28.0 

14.0 

13.3 

12.7 

70.2 

39.9 

35.1 

17.6 

16.7 

16.0 

105. 

59.8 

52.6 

26.3 

25.1 

23.9 

133. 

75.4 

66.3 

33.2 

31.6 

30.1 

166. 

94.2 

82.9 

41.4 

39.5 

37.7 

199. 

113. 

99.4 

49.7 

47.4 

45.2 

265. 

151. 

133. 

66.3 

63.2 

60.3 

332. 

188. 

166. 

82.9 

79.0 

75.4 

464. 

264. 

232. 

116. 

111. 

106. 

597. 

339. 

298. 

149. 

142. 

136. 

642. 

365. 

321. 

160. 

153. 

146. 

802. 

456. 

401. 

200. 

191. 

182. 

963. 

547.. 

481. 

241. 

229. 

219. 

The  above  table  is  arranged  to  show  the  amperes  per  motor  at 
different  voltages  for  several  sizes  of  motors  at  efficiencies  obtained  in 
ordinary  practice. 


HANDBOOK   ON   ENGINEERING. 


171 


Volts  Lost  at  Different  Per  Cent  Drop. 

Voltage  at  Lamp  or  Distribution  Point,  Top  Row. 
TABLE  No.  4. 


VOLTS 

52 

75 

ICO 

110 

220 

400 

i% 

.261 

.376 

.502 

.552 

1.10 

2.01 

\% 

.525 

.757 

1.01 

1.11 

2.22 

4.04 

\l% 

.787 

1-14 

1.52 

1.67 

3.35 

6.09 

2% 

1.06 

1.53 

2.04 

2.24 

4.48 

8-16 

H% 

1.33 

1.92 

2.56 

2.82 

5.64 

10.25 

3% 

1.61 

2.31 

3.09 

3.40 

6.80 

12.37 

4% 

2.16 

3.12 

4  =  16 

4.58 

9.16 

16.06 

5% 

2.73 

3.94 

5.26 

5.78 

11.57 

21.05 

K% 

3.31 

4.78 

6.38 

7.02 

14.04 

25.53 

7% 

3.91 

5.G4 

7.52 

8.27 

16.55 

30.10 

Z% 

4.52 

6o52 

8.69 

9.56 

19.13 

34.78 

3% 

5.14 

7o41 

9.89 

10.87 

21.75 

39.56 

10% 

5.77 

8o33 

11.11 

12.22 

24.44 

44.44 

12% 

7.09 

10.22 

13.63 

14o99 

29.99 

54.54 

13% 

7.76 

11.10 

14.04 

16.43 

32.87 

59.76 

U% 

8.46 

12.20 

16.27 

17.90 

35.81 

65.1 

15% 

9.17 

13.23 

17.64 

19.41 

38.82 

70.5 

20% 

13. 

18.75 

25. 

27.50 

55. 

100. 

25% 

17.33 

25. 

33.33 

36.66 

73.33 

133. 

The  above  table  shows  the  loss  in  voltage  between  dynamos  and 
distribution  point  at  different  per  cents  and  for  various  voltages. 


172 


HANDBOOK   ON   ENGINEERING. 


Volts  Lost  at  Different  Per  Cent  Drop. 

Voltage  at  Lamp  or  Distribution  Point,  Top  Row. 
TABLE  No.  4. 


500 

600 

800 

1000 

1200 

2000 

2.51 

3  01 

4.02 

5  02 

6.03 

10.05 

5  05 

6.66 

8.08 

10.10 

12.12 

20.2 

7.61 

9.13 

12.1 

152 

18.2 

30.4 

10  2 

12.2 

16.3 

20  4 

24.4 

40.8 

12  8 

15  3 

20.5 

25.6 

30.7 

51.2 

15.4 

18.5 

24.7 

30.9 

37.1 

61.8 

20.8 

24.9 

33.3 

41.6 

49  9 

83.3 

26.3 

31.5 

42.1 

52.6 

63.1 

105. 

31.9 

38.2 

-   51. 

63.8 

76.5 

127. 

37.6 

45.1 

60.2 

752 

90.3 

150. 

43.4 

52.1 

69.5 

86.9 

104. 

173. 

49.4 

59.3 

79.1 

98.9 

118. 

197. 

55.5 

66.6 

88.8 

111. 

133. 

222. 

61.7 

74.1 

98  8 

123. 

148. 

247. 

68.1 

81.8 

109. 

136. 

163. 

272. 

74.7 

89.6 

119. 

149. 

179. 

298. 

81.3 

97.6 

130. 

162. 

195. 

325. 

88.2 

105. 

141. 

176. 

211. 

352. 

125. 

150. 

200. 

250. 

300. 

400. 

166. 

200. 

266. 

333. 

400. 

606. 

By  adding  the  volts  given  .in  the  table  to  the  voltage  at  motor  or  lamp 
the  result  shows  the  voltage  necessary  at  dynamo  for  voltage  required 
at  point  of  distribution. 


HANDBOOK   ON   ENGINEERING. 


173 


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174 


HANDBOOK   ON   ENGINEERING, 


Approximate  Weight  and  Measurement  of  "  0.  K."  Triple  Braided 
Weatherproof  Copper  Wire. 

TABLE  No.  6. 


B.  &  S. 
Gauge  No. 

Feet 
per  Pound. 

Pounds 
per  1000  ft. 

Pounds 
Per  Mile. 

0000 

1.30 

767 

4050 

000 

1.59 

629 

3320 

00 

2.02 

495 

2610 

0 

2.45 

407 

2150 

1 

3.22 

310 

1640 

2 

.  4.00 

250 

1320 

3 

5.03 

199 

1050 

4 

6.10 

164 

865 

5 

7.43 

135 

710 

6 

9.00 

111 

587 

8 

13.54 

74 

390 

10 

18.85 

53 

280 

12 

28.54 

35 

185 

14 

40.61 

25 

130 

16 

60.00 

17 

88 

18 

75.43 

13 

70 

HANDBOOK   ON   ENGINEERING. 


175 


Table   Showing  Difference  Between  Wire  Gauges  in  Decimal  Parts 

TABLE  No.  7.  of  an  Inch. 


c 

c 

5«;i 

sea, 

h 
O 

a 

9 

III 

^s§ 

r*  tt  M 

SR 

JB 

• 

u 

2.2 

•03 
f« 

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£ 

Ci  >  M 

Tr*J 

g  O  Q 

M  fl 

is 

III 

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s5 

S££ 

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js  a  -so 

|| 

K 

0} 

P 

w  3 

o 
o 

* 

o 

MCO 

CQ 

00  cj  o  S3 

^SoS 

0  ;_, 

to 

22 

000000 

46 

000000 

00000 

.43 

.45 

00000 

0000 

".'46'" 

i454 

.393 

.4 

.4 

0000 

000 

.40964 

.425 

.362 

.36 

.372 

'...... 

000 

00 

.3648 

.38 

.331 

.33 

.348 

00 

0 

.32495 

.34 

.307 

.305 

.324 

o 

1 

.2893 

.3 

.283 

.285 

.3 

1 

2 

.25763 

.284 

.263 

.265 

.276 

2 

3 

22942 

.259 

.244 

.245 

.252 

3 

4 

.20431 

.238 

.225 

.225 

.232 

4 

5 

.18194 

.22 

.207 

.205 

.212 

5 

6 

.16202 

.203 

.192 

.19 

.192 

6 

7 

.14428 

.18 

.177 

.175 

.176 

7 

8 

.12849 

.165 

.162 

.16 

.16 

8 

9 

.11443 

.148 

.148 

.145 

.144 

.  .  .  .  

9 

10 

.10189 

.134 

.135 

.13 

.128 

10 

11 

.090742 

.   .12 

.12 

.1175 

.116 

11 

12 

.080808 

.Ki9 

.105 

.105 

104 

]2 

13 

.071961 

.095 

.092 

.0925 

.092 

13 

14 

.064084 

.083 

.08 

.08 

.08 

'"oss"" 

14 

15 

.057068 

.072 

.072 

.07 

.072 

.072 

15 

16 

.05082 

.065 

.063 

.061 

.064 

.065 

16 

17 

.045257 

.058 

.054 

.0525 

.056 

.058 

17 

18 

.040303 

.049 

.047 

.045 

.048 

.049 

18 

19 

.03589 

.042 

.041 

.039 

.04 

.04 

19 

20 

.031961 

.035 

.035 

.034 

.036 

.035 

20 

21 

.028462 

.032 

.032 

.03 

.032 

0315 

21 

22 

.025347 

.028 

.028 

.27 

.028 

.0295 

22 

23 

.022571 

.025 

.025 

.024 

.024 

.027 

23 

24 

.0201 

.022 

.023 

.0215 

.022 

.025 

24 

25 

.0179 

.02 

.02 

.019 

.02 

.023 

25 

26 

.01594 

.018 

.018 

.018 

.018 

.0205 

26 

27 

.014195 

.016 

.017 

.017 

.0164 

.01875 

27 

28 

.012641 

.014 

.016 

.016 

.0148 

.0165 

28 

29 

.011257 

.013 

.015 

.015 

.0136 

.0155 

29 

30 

.010025 

.012 

.014 

.014 

.0124 

.01375 

30 

31 

.008928 

.01 

.0135 

.013 

.0116 

.01225 

31 

32 

.00795 

.009 

.013 

.012 

.0108 

.01125 

32 

33 

.00708 

.008 

.011 

.011 

.01 

.01025 

33 

34 

.006304 

.007 

.01 

.01 

.0092 

.0095 

34 

35 

.005614 

.005 

.0095 

.009 

.0084 

.009 

35 

36 

.005 

.004 

.009 

.008 

.0076 

.0075 

36 

37 

.004453 

.0085 

.00725 

.0068 

.0065 

37 

38 

.C039b5 

.008 

.0065 

.006 

.00575 

38 

39 

.003531 

.0075 

.00575 

.0052 

.005 

39 

40 

.003144 

.007 

.005 

.0048 

0045 

40 

176 


HANDBOOK    ON    ENGINEERING. 


Weather 
proof  in- 
sulation. 


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HANDBOOK    ON    ENGINEERING.  177 

THE  STEAM  ENGINE. 

CHAPTER     XI. 
THE  SELECTION  OF  AN  ENGINE. 

There  are  so  many  conflicting  statements  in  regard  to  the 
merits  and  demerits  of  the  several  engines  placed  in  the  market 
that  one  is  often  confused  in  judgment,  and  scarcely  knows  how 
to  proceed  in  the  matter  of  selection, 

It  is  easy  to  advise  that  ' '  When  you  are  ready  to  buy,  select 
the  best  engine,  for  in  the  long  run  the  best  is  the  cheapest." 
No  one  would  pretend  to  deny  this  as  a  general  rule,  yet  there  are 
circumstances  which  so  materially  modify  this  rule  that  it  would 
seem  to  a  casual  observer  to  be  entirely  set  aside.  There  are 
localities  in  which  the  price  of  fuel  is  so  low  that  it  scarcely  war- 
rants the  doubling  of  the  price  on  an  engine  to  save  it ;  and  in 
such  localities  the  owners  usually  want  an  engine  of  the  very 
simplest  construction ;  hence,  they  almost  invariably  select  an 
ordinary  slide  valve  engine  with  a  throttling  governor.  This 
selection  is  made  for  several  reasons,  among  which  are  low  first 
cost,  simple  in  detail,  remoteness  from  the  manufacturer  or  from 
repair  shops. 

For  small  powers  in  which  it  is  desirable  that  the  investment 
be  as  low  as  consistent  with  commercial  success,  the  engine 
selected  should  be  fitted  with  a  common  slide  valve ;  this  will  in 
general  apply  to  all  engines  having  cylinders  eight  inches  or  less 
in  diameter. 

If  upon  a  thorough  canvass  of  the  situation,  it  then  be  thought 
advisable  to  employ  an  automatic  cut-off  engine,  the  next  ques- 
tion would  probably  be  whether  it  shall  be  fitted  with  a  positive, 
or  some  one  of  the  various  ' '  drop ' '  movements  now  in  the 
market. 

12 


178  HANDBOOK    ON    ENGINEERING. 

For  the  smaller  sizes,  say  8  to  24  inches  diameter  of  cylinder, 
it  will  perhaps  be  found  more  desirable  to  use  an  automatic  slide 
cut-off,  of  which  there  are  now  several  varieties  offered  through 
the  trade.  This  style  of  engine  has  the  advantage  of  being  low- 
priced,  efficient  and  economical. 

Small  engines  are  usually  required  to  run  at  pretty  high 
speed ;  there  is  a  very  decided  advantage  in  this  on  the  score  of 
economy,  as  a  small  engine  running  at  a  quick  speed  will  be  quite 
as  efficient  as  a  large  engine  running  at  a  slow  speed,  with  the 
further  advantage  that  the  former  will  not  cost  in  original  outlay 
more  than  about  two-thirds  of  the  latter,  while  the  cost  of  operat- 
ing will  be  no  greater  per  indicated  horse  power. 

The  slide  valve  is  still  used  to  the  almost  total  exclusion  of  all 
other  kinds  in  locomotives.  It  is  doubtful  whether  a  better  valve 
for  that  particular  use  can  be  devised.  It  is  simple,  efficient,  and 
readily  obeys  the  action  of  the  link  when  controlled  or  adjusted 
by  the  engineer.  For.  portable  engines  and  the  smaller  stationary 
engines  it  leaves  little  to  be  desired  in  point  of  simplicity. 

One  objection  to  a  slide  valve  is  that  it  cannot  readily  be  made 
to  cut  off  steam  at,  say,  half-stroke  or  less,  without  interfering 
with  the  exhaust.  In  ordinary  practice  |  to  -|  seems  to  be  where 
most  slide  valves  cut  off  as  a  minimum,  perhaps  J  would  repre- 
sent nearer  the  actual  average  conditions. 

It  can  easily  be  shown  that  this  is  very  wasteful  of  steam,  and 
consequently  not  economical  in  fuel ;  but  as  there  are  cases  in 
which  the  loss  in  fuel  is  fully  gained  by  other  advantages,  the 
ordinary  slide  valve  will,  in  all  probability,  continue  to  be 
used. 

High  speed  engines*  —  The  general  tendency  seems  now  to  be 
in  the  direction  of  a  horizontal  engine  with  a  stroke  of  medium 
length  having  a  rapid  piston  speed  and  a  rapid  rotation  of  crank 
shaft,  rather  than  a  longer  stroke  with  a  less  rate  of  revolution. 
This  rapid  movement  of  piston  and  crank  shaft  permits  the  use  of 


HANDBOOK    ON    ENGINEERING.  179 

small  fly-wheels  and  driving  pulleys,  and  thus  very  materially 
reduces  the  cost  of  an  engine  for  a  given  power. 

To  illustrate  this,  it  may  be  said  that  a  16x48  inch  engine 
using  steam  at  80  Ibs.  pressure  and  cutting  off  J  stroke,  running 
at  the  rate  of  60  revolutions  per  minute,  may  be  replaced  by 
an  engine  having  a  13  x  24  inch  cylinder,  running  at  the  rate  of 
200  strokes  per  minute,  the  pressure  of  steam  and  point  of  cut- 
ting off  remaining  the  same,  both  engines  being  non-condensing, 
and  representing  the  best  example's  of  their  kind.  The  differ- 
ence between  60  and  200  revolutions  per  minute  in  millwright 
work  is  very  great,  but  there  is  a  constantly  growing  demand  for 
an  engine  which  shall  meet  such  a  requirement  whenever  it 
shall  present  itself ;  by  this  is  not  to  be  understood  an  engine 
which  shall  be  used  at  either  speed  indiscriminately,  but  rather  a 
type  of  engine  which  shall  be  economical  in  fuel,  and  shall  be  of 
a  kind  by  which  the  rate  of  revolution  may  be  such  as  to  suit  the 
millwright's  work  without  loss  of  economy  in  working,  and  with- 
out excessive  outlay  for  the  engine  itself  in  proportion  to  power 
developed. 

Slow  speed  engines  are  designed  and  built  from  a  standpoint 
entirely  different  from  that  of  high  speed  engines  ;  in  the  former 
case  the  reciprocating  parts  are  made  as  light  as  possible,  con- 
sistent with  safety.  The  fly  wheel  is  large  in  diameter  and  made 
with  a  very  heavy  rim,  especially  is  this  the  case  with  auto- 
matic cut-off  engines  of  long  stroke  and  slow  revolution  of  crank 
shaft. 

In  high  speed  engines  the  reciprocating  parts  are  often  of  great 
weight,  in  order  to  insure  the  utmost  smoothness  of  running. 
The  piston  and  cross-head  are  made  of  unusual  weight  that  at  the 
beginning  of  the  stroke  they  may  require  a  large  part  of  the  steam 
pressure  to  set  them  in  motion ;  this  absorbing  of  power  at  the 
beginning  of  the  stroke  is  for  the  purpose  of  temporarily  storing 
it  up  in  the  reciprocating  parts  that  it  may  be  given  off  at  the 


180  HANDBOOK    ON    ENGINEERING. 

later  portions  of  the  stroke,  by  imparting  their  momentum  to  the 
crank ;  thus  at  the  beginning  of  the  stroke,  these  reciprocating 
parts  act  as  a  temporary  resistance,  but  once  in  motion  they  tend 
by  their  inertia  to  equalize  the  pressure  on  the  crank  pin,  and  so 
produce  not  only  smooth  running,  but  a  very  uniform  motion. 

Results  to  be  obtained  in  practice*  —  The  best  automatic  non- 
condensing  engines  furnish  an  indicated  horse  power  for  about 
three  pounds  of  good  coal^  depending  somewhat  upon  the  fitness 
of  the  engine  for  the  work  and  the  quality  of  the  coal.  With  a 
condenser  attached,  a  consumption  as  low  as  two  pounds  has  been 
reported,  but  this  is  an  exceptional  result,  2 J  pounds  may  be 
quoted  as  good  practice.  The  larger  the  engine  the  better  the 
showing,  as  compared  with  smaller  engines. 

For  ordinary  slide  valve  engines,  the  coal  burned  per  indicated 
horse  power  will  vary  from  9  to  12  Ibs.,  for  the  sake  of  illustra- 
tion, we  will  say  10  Ibs.,  and  that  the  engine  is  of  such  size  as 
would  require  for  a  year's  run  S3, 000  worth  of  coal;  now,  an 
ordinary  adjustable  cut-off  engine  with  throttling  governor,  ought 
to  save  at  least  half  that  amount  of  coal,  or  say  $1,500  per  year  ; 
if  the  best  automatic  engine  were  employed  using  21  Ibs.  of  coal 
per  horse  power,  a  further  saving  of  $750  per  year  could  be 
effected,  or  between  the  two  extremes  $2,250  per  year  in  saving 
of  coal,  without  interfering  in  any  way  with  the  power,  with  the 
exception,  perhaps,  that  the  automatic  engine  will  furnish  a  better 
power  than  the  former  engine.  It  is  easy  to  see  that  it  is  true 
economy  to  buy  the  best  engine  and  pay  the  extra  cost  of  con- 
struction, if  the  saving  of  fuel  is  an  element  entering  into  the 
question  of  selection. 

The  cost  of  an  engine  for  any  particular  service  is  always  to 
be  taken  into  consideration,  for  it  is  possible  to  contract  for  a 
certain  saving  of  coal  at  too  high  a  price,  not  simply  when  paid 
out  as  the  .original  purchase  money,  but  with  this  economy  of 
fuel,  the  purchaser  may  have  many  vexatious  and  damaging 


HANDBOOK    ON    ENGINEERING.  181 

delays  caused  by  the  breaking  of  the  automatic  mechanism  of  the 
engine.  All  such  delays  which  would  not  have  occurred  to  an 
ordinary  or  simpler  engine,  are  to  be  charged  against  any  saving 
credited  to  the  engine  which  failed  in  producing  a  regular  and 
constant  power.  Take  a  flouring  mill  for  example,  producing  400 
barrels  per  day  ;  it  is  easy  to  see  how  a  single  day's  stoppage 
would  interfere  with  the  trade  and  shipment  by  the  proprieters, 
yet  it  would  require  a  very  small  break  in  an  engine  that  would 
require  less  than  a  day  for  repairs. 

This  does  not  argue  against  high  grade  engines,  but  the  pur- 
chaser should  be  certain  that  the  engine  when  once  on  its  founda- 
tions shall  be  as  free  from  dangers  of  this  kind  as  any  other 
engine  of  similar  economy. 

There  are  engines  which  from  their  peculiar  construction 
appear  to  be  very  complex,  and  this  objection  is  often  urged 
against  them,  while  the  fact  is  the  complexity  is  apparent  rather 
than  real.  Take  the  Corliss  engine,  for  example;  it  is  doubtful 
whether  there  is  another  automatic  cut-off  engine  in  successful 
use  in  this  or  any  other  country  which  has  cost  less  for  repairs 
during  the  last  ten  or  twenty  years.  It  is  true  it  contains  a  great 
many  separate  pieces  in  the  valve  mechanism,  but  the  pieces 
themselves  are  simple,  durable,  easily  accessible  and  always  in 
sight.  These  several  parts  are  not  liable  to  excessive  wear,  but 
such  as  there  is  can  lie  readily  adjusted. 

The  engines  to  be  preferred  are  those  in  which  the  valve 
ad  justing  mechanism  is  outside  of  the  steam  chest  and  which  is  in 
plain  sight  at  all  times  when  the  engine  is  in  motion. 

Location  of  engine.  —  This  will  depend  upon  circumstances, 
but  it  is  far  from  true  economy  to  place  an  engine  in  a  dark  cellar, 
or  in  some  inconvenient  place  above  ground.  The  engine  as  the 
prime  mover,  should  have  all  the  care  and  attention  which  may  be 
needed  to  insure  regular  and  efficient  working. 

Machinery  in  the  dark  is  almost  sure  to  be  neglected.     If  the 


182  HANDBOOK    ON    ENGINEERING. 

design  of  the  building,  or  the  nature  of  the  business,  is  such  that 
the  engine  must  be  located  underground,  there  should  be  some 
provision  for  letting  in  the  daylight ;  the  extra  expense  incurred 
will  soon  be  saved  by  the  order,  cleanliness  and  fewer  repairs 
required,  following  neglect. 

The  engine  should  always  be  close  to,  but  not  in  the  boiler 
room.  Many  a  high-priced  engine  has  had  its  days  of  usefulness 
shortened  by  the  abrasive  action  of  fine  ashes  and  coal  dust 
coming  in  contact  with  the  wearing  surfaces.  There  should  always 
be  a  wall  or  tight  partition  between  the  engine  and  fire  room. 

The  foundations  for  an  engine  should  be  large  and  deep. 
Too  many  manufacturers  in  marking  dimensions  of  foundation 
drawings  for  engines,  make  them  altogether  too  shallow.  The 
stability  of  an  engine  depends  more  on  the  depth  than  on  the 
breadth  of  the  foundations.  Stone  should  be  used  for  founda- 
tions rather  than  brick,  but  if  the  latter  must  be  used  they  should 
be  hard  burned  and  laid  in  a  good  cement  rather  than  a  lime 
mortar.  If  the  bottom  of  the  pit  dug  for  the  engine  foundation 
be  wet,  or  the  soil  uncertain  in  its  stability,  it  is  a  good  plan  to 
make  a  solid  concrete  block  about  a  foot  and  a  half  thick,  on 
which  the  foundation  may  be  continued  to  the  top.  If  such  a 
concrete  block  be  made  with  the  right  kind  of  cement  it  will  be 
almost  as  hard  and  solid  as  a  whole  stone. 

The  most  economical  engine  is  the  one  in  which  high  pressure 
steam  can  be  used  during  such  portion  of  the  stroke  as  may  be 
necessary,  then  quickly  cut  off  by  a  valve  which  shall  not  inter- 
fere with  the  exhaust  at  the  opposite  end  of  the  cylinder,  and 
allow  the  steam  to  expand  in  the  cylinder  to  a  pressure  which 
shall  not  fall  below  that  necessary  to  overcome  the  back  pressure 
on  the  piston.  In  general,  the  most  successful  cut-off  engines 
use  the  boiler  pressure  for  a  distance  of  one-fifth  to  three-eighths 
of  the  stroke  from  the  beginning  ;  at  this  point  the  steam  is  cut 
off  and  allowed  to  expand  throughout  the  balance  of  the  stroke. 


HANDBOOK    ON    ENGINEERING. 


183 


The  gain  by  expansion  consists  in  the  admission  of  steam  at  a 
pressure  much  above  the  average  required  to  do  the  work,  and 
allowing  it  to  follow  but  a  small  portion  of  the  stroke,  then  ex- 
panding to  a  lower  than  the  average  pressure  at  the  end  of  the 
stroke.  The  mean  effective  pressure  on  the  piston  is  that  by 
which  the  power  of  the  engine  is  measured ;  hence,  it  follows  that 
the  higher  economy  is  to  be  reached,  other  things  being  equal,  where 
the  mean  effective  pressure  on  the  piston  is  highest  when  com- 
pared with  the  terminal  pressure,  or  the  pressure  at  the  end  of  the 
stroke.  In  order  to  get  this,  a  high  initial  pressure  is  used  ;  the 
steam  follows  as  short  a  distance  as  possible  to  keep  the  motion 
regular  under  a  load,  and  then  expanding  down  to  as  near  the 
atmospheric  pressure  as  possible. 

The  following  table  exhibits  at  a  glance  the  performance  of  a 
non-condensing  engine  cutting  off  at  different  portions  of  the 
stroke.  The  initial  pressure  of  steam  being  in  each  case  eighty 
pounds  per  square  inch. 

CUT-OFF    IN    PARTS    OF    THE    STROKE. 


1 

2 

3 

4 

5 

10 

10 

10 

10 

10 

Mean  effective  pressure    . 

18 

35 

48 

57 

65 

Terminal  pressure  .     .     . 

11 

20 

30 

39 

48 

Pounds  water,  per  h'r  per 

H.  P  

20 

21 

22 

23 

25 

Fractions  are  omitted  in  the  above  table  and  the  nearest  whole 
number  given. 

Governor*  —  Any  automatic  device  by  which  the  speed  of  an 
engine  is  controlled  may  properly  be  called  a  governor.  There 


184  HANDBOOK    ON    ENGINEERING. 

are  now  two  distinct  methods  by  which  the  steam  supplied  to  an 
engine  is  thus  brought  under  control.  The  first  is  usually  applied 
to  slide  valve  engines  having  a  fixed  cut-off,  and  consists  in  the 
adjustment  of  a  valve  by  which  the  pressure  of  steam  in  the 
cylinder  is  increased  or  diminished  in  order  to  maintain  a  con- 
stant rate  of  revolution  with  a  variable  load.  The  second  device 
consists  in  a  mechanism  by  which  the  whole  boiler  pressure  is 
admitted  to  the  cylinder,  which  is  allowed  to  follow  the  piston  to 
such  portion  of  the  stroke  as  will  maintain  a  regular  rate  of  revo- 
lution ;  the  steam  is  then  suddenly  cut  off  at  each  half  revolution 
of  the  engine,  thus  furnishing  a  greater  or  less  volume  of  steam  at 
a  constant  pressure.  Neither  of  these  two  varieties  of  governors 
will  act  until  a  change  in  the  rate  of  revolution  of  the  engine 
occurs,  and  this  change  will  either  admit  more  or  less  steam  as  it 
is  faster  or  slower  than  that  for  which  the  governor  is  adjusted. 
The  commonest  form  of  a  governor  consists  of  a  vertical  shaft  to 
which  are  hinged  two  arms  containing  at  their  lower  ends  a  ball 
of  cast  iron  ;  as  the  shaft  revolves  the  balls  are  carried  outward 
by  the  action  of  what  is  commonly  called  centrifugal  force ;  the 
greater  the  rate  of  revolution  the  further  will  the  balls  be  carried 
outward  ;  advantage  is  taken  of  this  property  to  regulate  the  ad- 
mission of  steam  to  the  engine.  The  action  of  the  balls  and  that 
of  the  valve  include  two  distinct  principles  and  should  be  consid- 
ered separately ;  an  excellent  valve  may  be  manipulated  by  an 
indifferent  governor  and  so  produce  unsatisfactory  results  ;  on  the 
other  hand,  the  governor  mechanism  may  be  satisfactory  in  its 
operation,  but  being  connected  with  a  valve  not  properly  balanced, 
is  likely  to  cause  a  variable  rate  of  revolution  in  the  engine. 

Fly- wheel.  —  The  object  in  attaching  a  fly-wheel  to  an  engine 
is  to  act  as  a  moderator  of  speed.  The  action  of  the  steam  in  the 
cylinder  is  variable  throughout  the  stroke,  against  which  the  rev- 
olution of  a  heavy  wheel  acts  as  a  constant  resistance  and  limits 
the  variations  in  speed  by  absorbing  the  surplus  power  of  the  first 


HANDBOOK    ON    ENGINEERING.  185 

portion  of  the  stroke,  and  giving  it  out  during  the  latter  portion. 
The  fly-wheel  is  simply  a  reservoir  of  power,  it  neither  creates  1101* 
destroys  it,  and  the  only  reason  why  it  is  attached  to  an  engine  is 
to  simply  regulate  the  speed  between  certain  permitted  variations 
which  are  necessary  to  cause  the  governor  to  act,  and  to  equalize 
the  rate  of  revolution  for  all  portions  of  the  stroke,  thus  convert- 
ing a  variable  reciprocating  power  into  a  constant  rotary  one.  It 
is  considered  good  practice  to  make  the  diameter  of  the  fly-wheel 
four  times  the  length  of  the  stroke  for  ordinary  engines,  in  which 
the  stroke  is  equal  to  twice  the  diameter  of  the  cylinder.  This 
may  be  taken  as  a  fair  proportion  in  engine  building,  and  furnishes 
a  wheel  sufficiently  large  to  equalize  the  strain  and  reduce  any 
variation  in  speed  to  within  very  narrow  limits,  if  the  engine  is 
supplied  with  a  proper  governor.  The  greater  the  number  of 
revolutions  at  which  the  engine  runs,  the  smaller  in  diameter  may 
be  the  fly-wheel,  and  it  may  also  be  largely  reduced  in  weight  for 
engines  developing  the  same  power. 

Horse-power*  —  By  this  term  is  meant  33,000  pounds  raised 
one  foot  high  in  one  minute.  The  horse-power  of  an  engine  may 
be  found  by  multiplying  the  area  of  the  piston  in  square  inches 
by  the  mean  effective  pressure ;  this  will  give  the  total 
pressure  on  the  piston ;  multiply  this  total  pressure  by  the 
length  of  the  stroke  of  the  piston  in  feet ;  this  will  give  the 
work  done  in  one  stroke  of  the  piston  ;  multiply  this  product  by 
the  number  of  strokes  the  piston  makes  per  minute,  which  will 
give  the  total  work  done  by  the  steam  in  one  minute ;  to  get  the 
horse-power,  divide  this  last  product  by  33,000.  From  this 
deduct,  say,  20  per  cent,  for  various  losses,  such  as  friction,  con- 
densation, leakage,  etc. 

CARE  AND  MANAGEHENT  OF  A  STEAM  ENGINE. 

It  is  to  be  supposed  to  begin  with  that  the  engine  is  correctly 
designed  and  well  made,  and  that,  after  a  suitable  selection  of  an 


186  HANDBOOK    ON    ENGINEERING. 

engine  for  the  work  to  be  done,  nothing  now  remains  except 
proper  care  and  management. 

Lubrication*  —  The  first  and  all-important  thing  in  regard  to 
keeping  an  engine  in  good  working  order  is  to  see  that  it  is 
properly  lubricated.  This  does  not  imply,  neither  is  it  intended 
to  encourage,  the  use  of  oil  to  excess  ;  all  that  is  needed  is  simply 
a  film  of  oil  between  the  wearing  surfaces.  It  is  marvelous  how 
small  a  quantity  of  oil  is  required  when  of  good  quality  and  con- 
tinuously applied.  There  are  several  self -feeding  lubricators  in 
the  market  which  have  been  tested  for  years  and  are  a  pronounced 
success ;  these  include  crank-pin  oilers,  in  which  the  oscillatory 
motion  of  the  oil  makes  a  very  efficient  self -feeding  device,  the 
flow  being  regulated  by  means  of  an  adjustable  opening  to  the 
crank-pin,  or  in  the  adjustment  of  a  valve  by  which  its  lift  is  reg- 
ulated by  each  throw  of  the  crank  ;  and  in  others  by  a  continual 
flow  through  a  suitable  tube  containing  a  wick  or  other  porous 
substance.  For  stationary  engines,  it  is  desirable  that  the  main 
body  of  the  oiler  be  made  of  glass  that  the  flow  of  oil  may  be 
closely  watched  and  adjusted  accordingly.  For  the  reciprocating 
and  rotary  parts  of  the  engine  $  a  modification  of  the  above  men- 
tioned oilers  may  be  used.  They  are  of  various  patterns  and 
devices  and  many  of  them  very  good.  It  is  also  a  good  plan  to 
have  some  device  by  which  the  cross-head  at  each  end  of  each 
stroke  will  take  up  and  carry  with  it  a  certain  amount  of  oil ;  for 
the  lower  half  of  the  slide  this  is  not  difficult  to  arrange  ;  for  the 
upper  side  an  automatic  feeder  placed  in  the  middle  of  the  slides 
will  provide  ample  lubrication. 

For  oiling  the  main  bearing  there  should  be  two  separate 
devices,  one  an  automatic  glass  oiler ;  and  in  addition,  a  large 
tallow  cup  attached  to  the  cap  of  the  bearing.  This  cup  should 
be  filled  with  tallow  mixed  with  powdered  plumbago ;  the  open- 
ings from  the  bottom  of  the  cup  to  the  shaft  should  be  not  less 
than  quarter-inch  for  small  engines,  and  three-eighths  to  half -inch 


HANDBOOK    ON    ENGINEERING.  187 

for  larger  ones ;  so  long  as  the  main  bearing  runs  cool  the  tallow 
will  remain  in  the  cup  unmelted ;  but  if  heating  begins,  the  tallow 
will  melt  and  run  down  on  the  surface  of  the  revolving  shaft,  and 
thus  provide  an  efficient  remedy  when  needed.  For  oiling  the 
valves  and  piston,  a  self -feeding  lubricator  should  be  attached  to 
the  steam  pipe  ;  this  by  a  continuous  flow  of  oil  will  be  found  not 
only  satisfactory  in  its  practical  working,  but  economical  in  the 
use  of  oil. 

In  selecting1  an  oil  for  an  engine,  it  is  in  general  better  to  use  a 
mineral  rather  than  an  animal  oil,  especially  for  use  in  the  valve 
chest  and  cylinder.  The  objection  to  an  animal  oil,  and  espe- 
cially to  tallow  or  suet,  is  that  it  decomposes  by  the  action  of  heat, 
often  coating  the  surface  of  the  steam  chest,  the  piston  ends  and 
the  cylinder  heads  with  a  deposit  of  hard  fatty  matter  ;  or  forms 
into  small  balls  not  unlike  shoemaker's  wax.  There  is  no  such 
decomposition  and  formation  in  connection  with  mineral  oils, 
which  may  now  be  had  of  uniform  quality  and  consistency,  and 
at  much  lower  prices  than  animal  oils. 

The  slide  valve  should  be  kept  properly  set  and  should  be 
examined  occasionally  to  see  that  the  face  and  seat  are  in  good 
condition.  So  long  as  this  is  the  case,  the  valve  mechanism  and 
the  valve  itself  must  be  let  alone  and  not  tampered  with. 

The  piston  packing"  will  need  looking  after  occasionally  to 
see  that  it  does  not  gum  up  and  stick  fast,  which  it  is  very  likely 
to  do  when  the  cylinder  is  lubricated  with  tallow  or  animal  oil. 

The  rings  should  fit  the  cylinder  snugly  and  should  be  under 
as  little  tension  as  possible  and  insure  perfect  contact.  If  the 
rings  are  set  out  too  tight  they  are  liable  to  scratch  or  cut  the 
cylinder  ;  if  too  loose,  the  steam  will  blow  through  from  one  end 
of  the  cylinder,  past  the  piston  and  into  the  other.  In  adjusting 
the  springs  in  the  piston,  care  must  be  exercised  that  the  adjust- 
ments are  such  as  will  keep  the  piston  rod  exactly  central,  to 
prevent  springing  the  rod,  or  causing  excessive  wear  on  the  stuf- 


188  HAND    BOOK    ON    ENGINEERING. 

fing  box.  There  are  several  packings  which  do  not  require  this 
adjustment,  the  rings  being  narrow,  and  either  expanding  by 
their  own  tension  or  by  means  of  springs  underneath.  The  only 
thing  to  be  done  with  such  a  packing  is  to  keep  it  clean,  and 
when  lubricated  with  a  mineral  oil  this  is  not  a  difficult  matter. 
If  it  groans,  take  rings  out  and  file  sharp  edges  off. 

The  stuffing  boxes  whether  for  the  piston  or  valve-stem  need 
to  be  looked  after  carefully,  and  to  prevent  leaking,  will  require 
tightening  from  time  to  time.  There  are  several  kinds  of  ready- 
made  packings  in  the  market,  containing  rubber,  canvas,  garlock, 
soapstone,  asbestos  and  other  substances  which  form  the  basis  of 
a  good  durable  packing.  These  can  be  had  in  sizes  suitable  for 
all  ordinary  purposes,  and  their  use  is  recommended.  In  the 
absence  of  any  of  these,  a  packing  made  of  clean  manila  or  hemp 
fiber  will  serve  a  useful  purpose.  Formerly  it  was  the  only  sub- 
stance used,  but  is  being  gradually  superseded  by  the  other  kinds 
mentioned  above.  In  packing  the  small  and  delicate  parts,  auch 
as  a  governor  stem,  a  good  packing  is  made  by  pleating  together 
three  or  more  strands  of  cotton  candle-wick.  This  is  soft,  pliable, 
free  from  anything  like  grit,  and  will  not  get  hard  until  soaked 
with  grease  and  baked  into  a  brittle  fiberless  substance  not  easily 
described. 

Crank-pins.  —  There  are  few  things  more  troublesome  to  an 
engineer  than  a  hot  crank-pin,  and  it  is  sometimes  very  difficult 
to  get  at  the  real  reason  why  it  heats.  Among  the  principal  rea- 
sons for  heating  are:  the  main  shaft  is  not  "  square  "  with  the 
engine,  or,  that  the  pin  is  not  properly  iitted  to  the  crank  ;  or, 
perhaps,  it  is  too  small  in  diameter  —  defects  which  are  to  be 
remedied  as  soon  as  practicable.  Heating  is  often  caused  by  the 
boxes  being  keyed  too  tightly,  or  by  insufficient  lubrication. 
There  are  now  several  good  self -feeding  lubricators  in  the  market 
which  will  supply  the  oil  to  a  crank-pin  continuously  ;  these  are 
recommended  rather  than  the  old  style  of  oil  cup,  which  way 


HANDBOOK    ON    ENGINEERING.  189 

not  only  uncertain,  but  doubtful  in  its  action.  Many  trouble- 
some crank-pins  have  been  cured  of  heating  by  this  simple  matter 
of  constant  lubrication.  When  the  crank-pin  is  rather  small  for 
the  engine  and  the  load  variable,  there  is  a  possibility  of  having 
a  hot  pin  at  any  time ;  it  is  advisable  to  have  ready  some 
simple  and  effective  expedient  to  be  applied  when  it  does  occur ; 
for  this  there  is  perhaps  nothing  better  and  safer  than  a  mixture 
of  good  lard  oil  and  sulphur. 

Connecting  rod  brasses. — -In  quick  running  engines  the 
brasses  should  be  litted  metal  to  metal ;  or,  if  this  is  not  desir- 
able, several  strips  of  tin  or  sheet  brass  should  be  inserted  be- 
tween them  and  keyed  up  tight.  This  gives  a  rigidity  to  a 
joint  which  is  difficult  to  secure  when  the  brasses  have  a  certain 
amount  of  play  in  the  strap.  It  is  a  common  practice  to  bore  the 
brasses  slightly  larger  than  the  pin,  so  that  when  fitted  to  it  the 
hole  shall  be  slightly  oval,  and  thus  permit  a  freer  lubrica- 
tion than  is  secured  by  a  close  fit  around  the  whole  circum- 
ference. 

Knocking. — There  are  several  causes  which,  combined  or 
singly,  tend  to  produce  knocking  in  steam  engines.  In  most 
cases  the, difficulty  will  be  found  to  be  in  the  connecting  rod 
brasses  ;  but  whether  in  the  crank-pin  end  or  at  the  cross-head  is 
not  easily  determined  in  all  cases.  A  very  slight  motion  will 
often  produce  a  very  disagreeable  noise  ;  the  remedy  is,  in  most 
cases,  very  simple,  and  consists  in  simply  tightening  the  brasses 
by  means  of  the  key  or  other  device  that  may  have  been  pro- 
vided for  their  adjustment.  In  adjusting  a  key  it  is  the  common 
practice  to  drive  it  down  as  far  as  it  will  go,  marking  with  a 
knife  blade  the  upper  edge  of  the  strap,  then  drive  the  key  back 
until  it  is  loose ;  after  which  drive  it  down  again,  until  the 
line  scratched  on  the  key  is  within  J  or  1  inch  of  the  top  of  the 
strap.  The  size  of  the  strap  joint  and  the  judgment  of  the  per- 
son in  charge  must  decide  the  best  distance.  This  may  be  done 


190  HANDBOOK    ON    ENGINEERING. 

at  both  ends  of  the  connecting  rod.  On  starting  the  engine,  the 
cross-head  and  crank-pin  must  be  carefully  watched,  and  upon 
the  slightest  indication  of  heating,  the  engine  should  be  stopped 
and  the  key  driven  back  a  little  further.  A  slight  warmth  is  not 
particularly  objectionable,  and  will,  as  a  general  thing,  correct 
itself  after  a  short  run.  Knocking  is  sometimes  occasioned  by  a 
misfit,  either  in  the  piston,  or  cross-head  and  the  piston  rod. 
These  connections  should  be  carefully  examined,  and  under  no 
circumstances  should  lost  motion  be  permitted  at  either  end  of 
the  piston  rod. 

If  the  means  of  securing  are  such  that  the  person  in  charge  can 
properly  fasten  the  piston  to  the  rod,  he  should  see  that  it  is  kept 
tight ;  if  not,  then  it  should  be  sent  to  the  repair  shop  at  once,  as 
there  is  no  telling  when  an  accident  is  likely  to  overtake  an  engine 
with  a  loose  piston. 

The  connection  between  the  piston-rod  and  cross-head  is  usu- 
ally fitted  with  a  key  -and  furnishes  a  ready  means  of  tightening 
the  joint,  if  proper  allowance  has  been  made  for  the  draft  of  the 
key.  In  case  there  has  not,  the  piston-rod  and  cross-head  should 
be  filed  out  so  that  the  draft  of  the  key  will  insure  a  good  tight 
joint  when  driven  down. 

The  main  bearing  should  be  examined  and  if  there  should  be 
too  much  lateral  movement  of  the  shaft,  the  side  boxes  might 
then  be  adjusted  until  the  shaft  turns  freely,  but  has  no  motion 
other  than  a  rotary  one.  The  cap  to  the  main  bearing  should  also 
be  carefully  examined,  as  it  may  need  screwing  down  and  thus 
prevent  an  upward  movement  of  the  shaft  at  each  stroke ;  this 
applies  more  particularly  to  quick  running  engines. 

Engines  which  have  been  in  use  for  some  time  are  likely  to  have 
a  knock  caused  by  the  piston  striking  the  head.  This  is  brought 
about  by  having  a  very  small  clearance  in  the  cylinder  and  in  no^ 
providing,  by  suitable  liners,  for  the  wear  of  the  connecting  rod 
brasses,  In  a  case  of  this  kind,  liners  should  be  inserted  behind 


HANDBOOK    ON    ENGINEERING.  191 

the  brasses  in  the  connecting  rod,  or  new  brasses  put  in,  which 
will  restore  the  piston  to  its  original  position. 

Knocking1  may  be  caused  by  defects  in  the  construction  of  the 
engine ;  such,  for  example,  as  not  being  in  line,  the  crank-pin  not 
at  right  angles  to  the  crank,  the  shaft  may  be  out  of  line,  etc. 

Whenever  the  cause  is  one  in  which  it  can  be  shown  that  it  is 
a  constructive  defect,  there  is  but  one  remedy,  and  that  is  the  re- 
placing of  that  part,  or  the  assembling  of  the  whole  until 
perfect  truth  is  had  in  alignment  of  all  the  parts.  This  will 
require  the  services  of  an  experienced  engineer  but  all  improperly 
fitting  pieces  should  be  replaced  by  new  ones  as  a  safeguard 
against  accident,  which  is  likely  sooner  or  later  to  overtake  badly 
fitting  pieces. 

If  the  boiler  is  furnishing  wet  steam,  or  priming,  so  as  to  force 
water  into  the  steam  pipe,  it  will  collect  in  the  cylinder  and  will 
not  only  cause  knocking,  but  on  account  of  its  being  practically 
incompressible  there  is  danger  of  knocking  out  a  cylinder  head, 
bending  the  piston-rod,  or  doing  other  damage  to  the  engine. 
The  cylinder  cocks  should  be  opened  to  drain  any  collected  water 
away  from  the  cylinder. 

Repairs*  —  Whenever  it  is  necessary  to  make  repairs  the  work 
should  be  done  at  once  ;  oftentimes  a  single  day's  delay  will  in- 
crease the  extent  and  cost  fourfold.  If  an  engine  is  properly 
designed  and  built,  the  repairs  required  ought  to  be  very  trivial 
for  the  first  few  years  it  is  run,  if  it  has  had  proper  care.  It  may 
be  said  in  reply  to  this  "  true,  but  accidents  will  happen  in  spite 
of  every  care  and  precaution."  That  accidents  do  occur  is  true 
enough ;  that  they  occur  in  spite  of  every  care  and  precaution  is 
not  true.  In  almost  every  case,  accidents  may  be  traced  directly 
back  to  either  a  want  of  care,  negligence,  or  to  a  mistake. 

Fitting-  slide-valves*  -7"  The  practice  of  fitting  a  slide-valve  to 
its  seat  by  grinding  both  together  with  oil   and  emery,  is  wrong 
and  should  never  be  resorted  to.     The  proper  way  to  fit  the  sur- 


192  HANDBOOK    ON    ENGINEERING. 

faces  is  by  scraping ;  this  insures  a  more  accurate  bearing  to 
begin  with,  and  will  also  be  entirely  free  from  the  fine  grains 
of  emery  which  find  their  way  and  become  imbedded  in  the 
pores  of  the  casting,  and  are  thus  liable  to  cut  the  valve  face  and 
destroy  its  accuracy.  The  scraping  of  the  valve  and  seat  has  a 
beneficial  effect  by  causing  the  removal  of  the  fine  particles  of 
iron,  which  are  loosened  by  the  action  of  the  cutting  tool  in  the 
planing  machine,  and  which  ought  to  be  fully  removed  before  the 
engine  leaves  the  manufacturers'  hands.  Aside  from  this,  it  is 
doubtful  whether  the  scraping  amounts  to  anything  practically, 
for  the  reason  that  the  cylinder  and  valve  are  fitted  cold,  and  their 
relative  positions  are  distorted  by  the  action  of  the  heat  of  the 
steam,  once  the  engine  is  in  use.  The  scraping  which  simply 
renders  the  valve  face  and  seat  smooth  and  hard  is  all  that  is 
sufficient  to  begin  with,  and  may  be  re-scraped  after  the  valve 
has  been  in  use  a  few  days,  should  it  be  found  necessary, 
which  will  not  often  -be  the  case  in  small  and  ordinary  sized 
engines. 

Eccentric  straps  are  likely  to  need  repairs  as  soon  as  any- 
thing about  an  engine.  They  should  be  carefully  watched  at 
all  times.  If  they  are  likely  to  run  hot,  it  is  also  probable 
there  is  more  or  less  abrasion  or  cutting  going  on,  and  if 
prompt  measures  are  not  taken  to  arrest  itr  they  are  likely  to 
cut  fast  to  the  eccentric,  and  a  breakage  is  sure  to  occur. 

When  the  straps  begin  to  heat,  the  bolts  should  be  slackened 
a  little,  and  at  night,  or  perhaps  at  noon,  the  straps  should  be 
taken  off  and  all  cuttings  carefully  removed  with  a  scraper 
(not  with  a  file)  ;  the  rough  surfaces  on  the  eccentric  should 
be  removed  in  the  same  manner. 

The  straps  should  be  run  loose  for  a  few  days,  gradually 
tightening  as  a  good  wearing  surface  is  obtained. 

The  main  bearing,  if  neglected,  is  a  very  troublesome  journal 
to  keep  in  order.  The  repairs  generally  needed  are  those  which 


HANDBOOK    OX    EXCJINKKKING.  11)3 

attend  overheating  and  cutting.  The  shaft,  whenever  possible, 
should  be  lifted  out  of  the  bearing,  and  both  the  shaft,  bottom  of 
main  bearing  and  side  boxes,  carefully  scraped  and  made  perfectly 
smooth.  It  sometimes  occurs  that  small  beads  of  metal  project 
above  the  surface  of  the  shaft  which  are  often  so  hard  that  neither 
a  scraper  nor  file  will  remove  them  ;  chipping  is  then  resorted  to 
and  the  fitting  completed  with  a  file  and  line  emery  cloth. 

Heating  of  journals*  —  A  very  common  cause  for  the  heating 
of  journals  having  brasses  and  boxes  composed  of  two  halves,  is 
that  both  halves  alter  their  shape  from  causes  attending  their 
wear.  Thus,  most  engineers  will  have  noticed  that,  although 
there  is  no  wear  between  the  sides  of  a  brass  and  the  jaws  of  a 
box,  yet  in  time  the  brass  becomes  a  loose  fit  in  the  box.  Now, 
since  the  sides  of  the  brass  have,  when  fitted,  no  movement  in  the 
box,  it  is  evident  that  this  cannot  have  proceeded  from  wear  be- 
tween those  surfaces,  and  it  remains  to  find  what  causes  this 
looseness.  Most  engineers  will  also  have  observed  that  though 
the  bottom  or  bedding  surfaces  of  a  brass  .and  of  the  box  may 
have  been  carefully  filed  to  fit  each  other  when  new,  yet  if  in  the 
course  of  time  the  brasses  be  taken  out  and  examined,  and  more 
especially  the  bottom  brass  that  receives  the  weight,  the  file  marks 
will  become  effaced  on  all  parts  where  the  surfaces  have  bedded 
together  well,  the  surface  having  a  dull  bronze  and  condensed 
appearance.  This  is  caused  by  the  vibrations  under  pressure  hav- 
ing condensed  the  metal.  Now,  this  condensation  of  the  metal 
moves  or  stretches  it,  and  causes  the  sides  of  the  brass  to  move 
away  from  the  sides  of  the  box,  and,  consequently,  to  close  upon 
the  journal,  creating  excessive  friction  that  may  often,  and  very 
often  does,  cause  heating.  It  is  for  this  reason  that  on  such 
brasses  the  sides  of  the  brass  boxes  are,  by  a  majority  of  engi- 
neers, eased  away  at  and  near  the  joint,  and  it  follows  from  this 
cause  the  same  easing  away  is  a  remedy. 

Governor*  —  It  not  inf req  uently  occurs  that  after  an  ordinary 

13 


194  HANDBOOK    ON    ENGINEERING. 

throttling  engine  has  been  used  a  few  years,  the  speed  becomes 
variable  to  such  a  degree  that  it  interferes  with  the  proper  run- 
ning of  the  machinery.  This  occurrence  can  generally  be  traced 
directly  to  the  governor.  When  it  does  occur,  the  governor 
should  be  taken  apart  and  thoroughly  examined  ;  if  the  needed 
repairs  are  such  as  can  be  easily  made  in  an  ordinary  repair  shop, 
they  should  be  made  at  once ;  if  not,  a  new  governor  should  be 
purchased.  The  price  of  governors  is  now  so  low  that  it  is  better 
and  more  economical  to  buy  a  new  one  than  lose  the  time  and 
pay  the  bills  for  repairing  an  old  one. 

AUTOMATIC  ENGINES. 

In  the  care  and  management  of  this  class  of  engines,  it  is  diffi- 
cult to  say  just  what  particular  attention  they  need,  owing  to  the 
variety  of  styles  and  the  peculiarities  of  each.  As  a  rule,  how- 
ever, they  require  first,  to  be  kept  well  oiled ;  second,  to  be  kept 
clean  ;  third,  to  be  kept  well  packed  ;  and  fourth,  to  be  let  alone 
nights  and  Sundays.  There  is  little  doubt  that  there  has  been 
more  direct  loss  resulting  from  a  ceaseless  tinkering  with  an 
engine  than  results  from  legitimate  wear  and  tear  to  which  the 
engine  is  subjected.  The  writer  does  not  wish  to  be  understood 
as  saying  that  builders  of  this  class  of  engines  are  infallible ;  it 
might  be  difficult  to  prove  any  such  assertion  in  case  it  was  made  ; 
but  it  may  be  said  with  truth,  that  the  engines  of  this  class  now 
in  the  market  are  carefully  designed,  well  proportioned,  of  good 
materials  and  workmanship,  and  as  examples  of  mechanism  are 
entitled  to  take  very  high  rank.  The  writer  knows  of  several 
engines  of  this  class  which  have  not  cost  their  owners  for  repairs 
so  much  as  five  dollars  in  five  years'  constant  use.  It  is  essential 
to  the  economical  working  of  these  engines  that  the  cut-oft' 
mechanism  be  in  good  order  and  properly  adjusted.  Whenever 
the  valves  need  resetting,  the  final  adjustment  should  be  made 


HANDBOOK    ON    ENGINEERING.  HIT) 

with  a  load  on  the  engine  and  with  the  indicator  attached  to  the 
cylinder,  the  valves  being  set  by  the  card  rather  than  by  the  eye. 
No  general  rule  can  be  given  for  setting  the  valves,  as  the  prac- 
tice varies  with  the  size  and  speed  of  the  engine  ;  nor  is  any  rule 
needed,  for  the  indicator  will  furnish  all  the  data  required.  The 
adjustments  may  then  be  made  so  as  to  secure  prompt  admission, 
sharp  cut-off,  prompt  release,  and  the  proper  compression. 

TO  FIND  THE  DEAD  CENTERS. 

When  setting  the  valve  of  an  engine  by  measuring  the  lead,  as 
is  the  usual  method,  it  is  necessary  that  the  crank  be  accurately 
placed  on  the  dead  centers  at  each  end  of  the  stroke.  Sometimes 
an  engineer,  when  adjusting  the  valves  of  his  engine,  will  attempt 
to  place  the  crank  on  the  dead  center  by  watching  for  the  point 
at  which  the  travel  of  the  cross-head  stops,  or  by  the  appearance 
of  the  connecting-rod  as  related  to  the  crank.  These  methods  are 
totally  unreliable  for  obtaining  accurate  results,  especially  the 
first  one  mentioned.  The  travel  of  the  cross-head  and  the  piston 
near  the  point  of  reversal  of  motion  is  very  slow  when  compared 
with  the  valve.  The  velocity  of  travel  of  the  valve  is  at  nearly 
its  maximum  amount  when  the  crank  is  on  the  dead  center,  and  a 
slight  error  in  finding  the  dead  center  point  makes  a  very  appre- 
ciable error  in  the  position  of  the  valve,  with  a  subsequent  error 
in  its  proper  setting. 

There  are  several  methods  for  finding  the  dead  center.  The 
method  that  can  be  recommended  and  the  one  that  should  always 
be  used  when  the  dead  center  of  an  engine  is  to  be  found  is  that 
familiarly  known  as  "  tramming."  The  dead  centers  when  found 
by  this  method,  are  geometrically  accurate,  no  matter  if  the  engine 
is  out  of  level  or  if  the  shaft  is  above  or  below  the  axis  of  the 
cylinder.  Some  simple  tools  are  required  which  are  generally 
available,  with  the  exception  of  the  trams,  which  may  be  readily 


UN; 


HANDBOOK    ON     KN(J  IX  KK1JI  N(I . 


made  for  the  purpose.  Two  trams  are  required,  one  of  which 
should  be  6"  or  7"  long  and  the  other  about  24"  or  30",  as  the 
condition  may  require.  The  smaller  tram  may  be  made  of  {" 
steel  wire  with  the  points  turned  over  at  right  angles  to  the  body, 
so  as  to  project  about  1".  The  points  should  be  sharpened  so 
that  a  hair  line  may  be  drawn  by  them.  The  larger  tram  should 
be  made  from  rod  of  at  least  f "  diameter  and  the  points  made  in 
the  same  way  as  for  the  smaller  tram.  Oftentimes,  the  long  tram 


Finding  the    Dead  Center. 

is  made  with  one  leg  longer  than  the  other,  on  account  of  being 
handier  to  reach  some  stationary  part,  but  this  is  a  minor  point, 
which  has  nothing  to  do  with  the  principle  to  be  described.  The 
other  tools  required  are  a  light  hammer,  a  prick-punch,  a  pair  of 
10"  or  12"  wing  dividers  and  a  hermaphrodite  caliper,  or  a  scrib- 
ing block.  A  piece  of  chalk  will  also  be  found  convenient  to 
facilitate  scribing  lines  on  the  metal  parts  with  the  trams  or 
dividers. 

Having  the  necessary  tools,  we  are  ready  to  begin  operations, — 
you  may  start  at  either  end  of  the  stroke,  as  circumstances  may 
favor.  The  fly-wheel  is  turned  so  that  the  crank  stands  at 
about  the  angle  shown  in  the  accompanying  illustration,  which 


HANDBOOK    ON    ENGINEERING.  1<>7 

may,  however,  l>e  approximated  as  the  operator  may  desire.  The 
effort  made,  being  to  give  sweep  enough  to  the  cross-head  to 
allow  accurate  measurements  and  still  not  have  such  an  excessive 
arc  on  the  fly-wheel  as  to  make  its  bisection  difficult. 

A  prick  mark  is  made  on  the  guides,  or  some  convenient  sta- 
tionary point,  as  at  /;?,  and  an  arc  struck  on  the  cross-head  with 
the  small  tram.  At  the  same  time,  an  arc  is  scribed  on  the  rim 
of  the  fly-wheel  at  6r,  using  some  convenient  point  for  the  lower 
point  of  the  tram  as  at  K.  The  fly-wheel  is  now  turned  until 
the  crank  passes  the  center  and  the  cross-head  travels  back  until 
the  scribed  line  will  coincide  exactly  with  the  point  of  the  tram 
when  held  in  the  same  position  as  in  the  first  case.  When  this 
point  has  been  reached,  the  wheel  is  stopped  and  a  second  arc  is 
scribed  on  the  fly-wheel  rim  at  F  with  the  tram  ,/.  The  herma- 
phrodite caliper,  or  the  scribing  block,  is  now  used  to  scribe  a 
concentric  line  I)  E  on  the  fly-wheel  rim  and  the  arc  C  F  is 
bisected  with  the  dividers.  When  the  center  //  has  been  accur- 
ately located,  it  should  be  carefully  prick-marked.  The  scribing 
of  the  concentric  line  D  E  is  a  refinement  that  is  not  strictly 
necessary  if  care  be  taken  to  locate  the  points  of  the  dividers  at 
the  same  distance  from  the  outer  periphery  of  the  wheel  in  each 
instance  when  finding  the  center  H.  The  marks  left  by  the  lathe 
tool  will  sometimes  be  plain  enough  for  a  guide.  When  the  center 
H  has  been  found,  the  fly-wheel  is  turned  so  that  the  point  of  the 
tram  will  fall  into  the  prick-mark  //  when  its  lower  end  is  in  the 
stationary  point  K.  When  this  condition  is  effected,  the  crank 
is  exactly  on  the  dead  center  and  the  position  of  the  valve  may 
be  taken  with  confidence  that  its  location  at  the  dead  center  point 
is  accurately  found.  The  same  procedure  is  followed  to  place  the 
crank  on  the  dead  center  at  the  opposite  end  of  the  stroke. 

The  cut  on  page  198  is  an  elevation  of  Tandem  Compound 
Engine,  showing  engine  erected  on  brick  foundation.  It  also 
shows  a  line  through  cylinders ;  also  a  line  over  the  shaft. 


198 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEEKING. 

These  lines  are  used  in  the  erection  of  a  new  engine,  or  to  line 
up  an  old  one,  or  with  an  engine  that  is  out  of  line.  The  cut  also 
shows  how  the  foundation  is  made;  also  how  the  anchor  bolt 
is  fastened. 

The  cut  on  page  200  shows  how  to  pipe  a  Twin  Tandem 
Compound  Condensing  Engine.  The  plan  shows  two  receivers, 
heaters,  relief  valves,  gate  valves,  etc.,  and  is  so  arranged 
that  either  side  can  be  run  independently  of  the  other.  It 
also  shows  how  to  line  a  pair  of  these  engines  up  by  following 
the  lines  and  noting  the  distance  between  each  line.  An  engineer 
would  have  no  trouble  in  lining  up  a  pair  of  these  engines. 

HOW  TO  LINE   AN  ENGINE. 

The  method  followed  when  lining  different  types  of  engines, 
such  as  vertical,  horizontal,  portable,  etc. :— 

The  method  followed  in  lining  any  piston  engine  is  essentially 
the  same  in  all  cases,  as  far  as  determining  when  adjustments  are 
needed.     The  method  of  making  the  adjustments  after  the  char- 
acter and  amount  of  them  is  determined,  depends  entirely  on  the 
construction  of  the  engine,  and  will  necessarily  have  to  be  deter- 
mined in  each  individual  case.     Lining  an  engine  consists  of    ad- 
justing the  guides   so  they   shall   be  parallel  to  the   bore  of  the 
cylinder,  and  in   such   a  position  that  the   center  of    the   piston 
socket  of  the  cross-head  shall  coincide  with  the  axis  of  the  cylin- 
der.    Under  these  conditions  only,  can  the  piston  and  cross-head 
travel  through  the  stroke  freely,  and  without  distorting  any  of  the 
parts.     After  this   adjustment  has  been  made,  the  truth  of  the 
right-angle  position  of  the  shaft   must    be  determined  as  being 
"out  of  square;  "this   will  make  an    engine  run  badly,  and  is 
often  the  unsuspected   cause  of    much  trouble  to  engineers.     We 
will  assume  that  we  have  an  engine  with  four-bar   or  locomotive 
guides,  and   that  the  connecting  rod,  cross-head,  back  cylinder 


200  HANDBOOK    ON    ENGINEERING. 


rr 


HANDBOOK    ON     KNUINKKKING  „ 


201 


head  and  piston  have  been  removed.  If  the  engine  is  of  the 
horizontal  type,  the  iirst  step  will  properly  be  to  ascertain  if  the 
engine  is  level  on  the  foundation,  and  if  not,  proceed  to  make  it 
so.  After  having  leveled  the  engine,  stretch  a  smooth  linen 
line,  as  shown  in  Fig.  1,  through  the  bore  of  the  cylinder  and 
the  stuffing  box,  to  a  point  beyond  the  shaft,  where  it  should  be 
attached  to  an  iron  rod  driven  into  the  floor.  The  other  end  is 
fastened  to  a  cross-bar  bolted  across  the  face  of  the  cylinder  to 


fig.  •% 


two  of  the  studs,  as  shown  in  Fig.  4,  or  the  bar  may  preferably 
be  somewhat  longer  than  one-half  of  the  diameter  of  the  cylinder, 
and  with  a  saw  cut  for  a  short  distance  lengthwise  at  the  inner 
end.  In  this  case,  it  is  held  by  only  one  of  the  cylinder  studs 
and  can  be  somewhat  more  easily  adjusted.  The  line  or  cord  is 
adjusted  to  approximately  the  proper  position,  and  is  drawn  taut 
and  fastened  through  the  cross-bar  by  being  tied  to  a  short  stick 
that  is  too  long  to  pass  through  the  hole.  In  this  position  it  is 
held  by  the  friction,  and  can  be  readily  adjusted  to  the  required 
position.  An  assistant  is  required  to  move  the  line  in  the  direc- 
tions indicated,  as  the  work  proceeds,  and  then  you  are  ready  to 
center  it  in  the  cylinder.  The  only  tool  required  for  this  purpose 
is  a  light  pine  stick  of  slightly  less  length  than  the  radius  of  the 


202  HANDBOOK    ON    ENGINEERING. 

bore,  and  it  should  have  an  ordinary  pin  pushed  into  the  head  for 
a  u  feeler."  Now  adjust  the  line  in  the  cylinder  so  that  the  head 
of  the  pin  will  just  tick  the  line  from  four  points  of  the  counter- 
bore,  which  is  always  the  part  of  the  cylinder  to  work  from,  as  it 
is  not  affected  by  the  wear.  The  line  should  then  be  adjusted 
to  the  center  of  the  other  end  of  the  cylinder,  but  not  from  the 
stuffing  box,  as  this  is  likely  to  be  out  of  center  somewhat. 
Make  the  adjustment  at  this  end  from  the  counterbore,  if  pos- 
sible, the  same  as  in  the  first  instance,  and  then  it  will  be  neces- 
sary to  try  the  position  of  the  line  in  the  back  end  of  the  cylinder, 
as  the  changes  made  at  the  other  end  will  affect  it  slightly.  After 
the  line  is  truly  centered,  you  are  ready  to  adjust  the  guides. 
With  some  types  of  cross-heads,  it  is  possible  to  use  the  cross- 
head  for  determining  the  proper  location  of  the  guides,  but  with 
the  ordinary  form,  such  as  shown  in  Fig.  2,  this  cannot  be  done, 
but  you  will  need  a  tool  similar  to  that  shown  in  Fig.  3,  which 
consists  simply  of  a  piece  of  flat  iron  long  enough  to  reach  across 
the  guides,  and  having  a  hole  drilled  and  tapped  in  the  center  for 
the  thumb-screw.  This  thumb-screw  is  adjusted  so  that  its  point 
is  the  same  distance  from  the  lower  side  of  the  bar,  as  the  lower 
face  of  the  wings  of  the  cross-head  are  from  the  center  of  the 
piston  socket.  To  find  this  distance,  lay  a  straight  edge  across 
the  end  of  the  cross-head  and  draw  the  line  A  B,  and  then,  hav- 
ing found  the  center  of  the  hole,  the  measurement  may  be  accur- 
ately taken.  The  lower  guides  are  now  adjusted  by  the  tool,  so 
that  the  point  of  the  screw  will  tick  the  line  throughout  the 
length,  and  then  the  top  guides  are  put  in  position  with  the  cross- 
head  in  place  and  adjusted  for  a  proper  working  fit. 

Before  removing  the  line  from  the  cylinder,  however,  the  shaft 
should  be  tested  for  the  truth  of  its  right-angle  position,  which 
may  be  done  by  calipering  between  the  crank  disc  and  the  line  at 
the  points  H  and  7.  If  the  distances  are  equal,  the  shaft  is 
square  with  the  bore  of  the  cylinder,  providing,  of  course,  that 


HANDBOOK    ON    ENGINEERING.  203 

the  disc  is  faced  true  with  the  slmft.  If  there  is  any  doubt  as  to 
its  accuracy,  turn  the  shaft  as  nearly  half  way  around  as  the 
crank-pin  will  admit  without  disturbing  the  line.  Then  caliper 
the  distance  of  a  point  on  the  disc  that  will  not  be  far  removed 
from  the  first  position,  thus  reducing  the  chance  for  error.  If 
the  shaft  shows  "  out,"  move  the  outward  bearing  until  the  meas- 
urements show  equal  in  both  positions.  The  horizontal  truth  of 
the  shaft  can  be  found  by  laying  a  level  on  it,  and  if  "out," 
raise  or  lower  the  out-board  bearing  until  the  level  shows  fair. 
Work  of  this  kind  requires  skill  and  patience  and  belongs  prop- 
erly to  the  sphere  of  the  chief  engineer.  It  requires  a  delicacy  of 
touch  and  an  appreciation  of  what  is  meant  by  close  measurement 
that  can  come  only  through  experience.  In  .centering  the  line, 
one  should  be  able  to  detect  when  it  is  as  little  as  T^Q-  of  an  inch 
out  of  center.  A  piece  of  ordinary  tissue  paper  is  about  .00125 
inch  thick.  A  man  should  be  able,  therefore,  to  adjust  a  line  so 
accurately  that  if  the  "  feeler,"  with  one  or  more  pieces  of  the 
paper  under  it,  just  clips  the  line,  it  will  miss  the  line  when  one 
thickness  is  removed.  While  it  may  not  always  be  necessary  to 
work  as  closely  as  this,  a  person  cannot  expect  to  line  up  engines 
successfully  until  he  has  a  full  knowledge  of  what  this  degree  of 
accuracy  means. 


204 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING.  205 


CHAPTER     XIa. 

DIRECTIONS    FOR    SETTING   UP,  ADJUSTING    AND    RUNNING 
THE  IMPROVED  CORLISS  STEAM  ENGINE. 

Location  of  foundation*  —  The  foundation  must  beat  right 
angles  with  main  line  shaft.  If  main  line  shaft  is  not  already  in 
position,  then  foundation  must  be  set  by  two  points,  located  and 
connected  with  a  line  parallel  with  the  buildings,  and  at  right 
angles  to  an  imaginary  line  through  center  of  cylinder. 

Foundation  plans  should  show  all  center  lines.  If  a  templet 
is  furnished  to  locate  the  foundation  accurately  for  the  mason,  the 
center  line  of  engine  cylinder  and  guides  and  right  angle  for 
crank  center  are  drawn  thereon. 

Cap  Stones*  —  Examine  carefully  the  lap  faces  of  cap  stones 
and,  if  necessary,  have  them  trimmed  off  by  cutter  or  mason,  so 
that  each  is  true  and  level,  and  in  exactly  the  plane  shown  in 
formation  plan. 

Cylinders  and  frame*  —  Put  engine  cylinder  and  frame  in 
position  and  bolt  them  together. 

Lining  off  crank  shaft  and  out-end  bearing*  —  Stretch  a 
line  at  right  angles  to  main  center  line,  through  main  bearing  to 
represent  center  line  of  crank  shaft.  See  that  this  line  is  exactly 
in  the  center  and  level.  By  this  line  place  out-end  bearing  square 
and  true.  Put  crank  shaft  in  its  bearings  after  bottom  box  has 
been  placed  in  main  bearings.  Insert  quarter  boxes  and 
adjusting  wedges  into  main  bearing  and  put  cap  on. 

To  ascertain  that  shaft  is  at  exact  right  angles  to  main  center 
line,  turn  engine  shaft  until  the  crank  pin  comes  nearly  to  the  main 


206  HANDBOOK    ON    ENGINEERING. 

center  line,  then  with  a  pair  of  calipers,  or  rule,  measure  from 
shoulder  of  crank-pin  to  line,  and  after  noting  this  distance,  turn 
the  crank  back  towards  opposite  center  until  pin  is  in  same 
relative  position  to  line,  and  measure  again.  If  both  measurements 
do  not  correspond,  out-end  bearing  must  be  moved  either  way  as 
required,  until  measurements  show  equal.  Then  take  up  slack 
around  shaft  in  main  bearing,  being  careful  not  to  force  the 
adjusting  wedge  too  tight. 

Fly- wheels.  —  The  fly-wheel  is  next  placed  on  shaft  and  firmly 
keyed  in  position. 

Placing  valve  gear.  —  Steam  and  exhaust  valve  covers  or  bon- 
nets on  valve  gear  side  are  next  bolted  to  place,  taking  care  that 
no  dirt  or  foreign  substance  gets  between  the  surface  underneath 
the  covers. 

Valve  stems  are  inserted  from  opposite  or  front  of  cylinder  and 
the  valves  put  in  after  them,  the  F  head  of  valve  stem  entering 
slot  in  valve.  Couple  up  all  valve  gear  parts,  i.  e.,  disc  plate, 
valve-stem  cranks,  valve-connecting  rods,  dash  pots  and  dash-pot 
rods,  valve-rod  rocker,  eccentric  and  straps  on  crank-shaft,  first 
and  second  eccentric  rods.  The  dash  pots  should  be  thoroughly 
cleaned  and  oiled  before  putting  in  place. 


ADJUSTMENT  OF  CORLISS  VALVE  GEAR  WITH  SINGLE  AND 
DOUBLE  ECCENTRICS. 

A  brief  description  of  the  essential  parts  of  the  Corliss  engine 
valve  gear  will  assist  in  obtaining  a  clear  conception  of  the 
subject. 

When  a  single  eccentric  drives  both  steam  and  exhaust  valves 
the  range  of  cut-off  is  limited  to  about  half  the  piston  stroke. 
This  will  become  obvious  by  considering  the  following  necessary 
conditions :  — 


HANDBOOK    ON    ENGINEERING. 


207 


After  the  eccentric  has  reached  the  extreme  of  its  throw  as 
shown  in  Fig.  2  in  either  direction  all  valve  gear  motions  are 
reversed . 


Fig.  2. 

The  steam  valve  must  be  released  before  the  eccentric  motion 
is  reversed,  for  if  the  hook  does  not  strike  the  knock-off  cam 
during  its  forward  motion,  it  cannot  strike  it  during  its  return 
motion. 

The  maximum  exhaust  opening,  or  the  middle  of  the  exhaust 
period,  must  occur  when  the  eccentric  is  at  the  extreme  of  its 
throw  as  in  Fig.  2. 

Now,  in  order  to  release  the  expanded  steam  in  the  cylinder 
before  the  commencement  of  the  return  stroke  and  to  secure  the 
exhaust  closure  a  little  before  the  end  of  the  return  stroke,  the 
middle  of  the  exhaust  period  or  the  extreme  of  the  eccentric 
throw  must  evidently  occur  before  the  middle  of  the  return 
stroke,  and,  therefore,  the  extreme  throw  of  the  eccentric  in  the 
opposite  direction  must  occur  before  the  middle  of  the  forward 
stroke,  and  the  valve  must  be  released  before  this  point  is  reached 
if  released  at  all. 

It  will  be  understood  from  the  foregoing  that  late  release  and 
late  exhaust  closures  are  conditions  imposed  by  the  single 
eccentric  valve  gear,  and  these  conditions  agree  very  well  with 
moderate  rotative  speed  ;  but  at  higher  speed  earlier  release  and 


208  HANDBOOK    ON    ENGINEERING. 

more  compression  may  be  required.  This  may  be  effected  by 
moving  the  eccentric  forward  on  the  shaft,  but  the  reversing  of 
the  steam  valve  motion  would  then  occur  at  an  earlier  stage  of 
the  forward  stroke  and  the  range  of  cut-off  would  be  correspond- 
ingly shortened.  Earlier  exhaust  closure  could  be  had  by  giving 
the  exhaust  valve  more  lap,  but  this  would  involve  a  later  release 
of  the  expanded  steam  at  the  end  of  the  stroke.  On  the  other 
hand,  shortening  the  exhaust  lap  would  give  earlier  release  but 
insufficient  or  no  compression. 

In  Fig's*  3  and  4  similar  capital  letters  of  reference  indicate 
the  same  parts  of  the  mechanism. 

Fig.  3  shows  all  the  essential  parts  of  the  valve  gear.  The 
steam  valves  work  in  the  chambers  S  S  and  the  exhaust  valves 
work  in  the  chambers  E  E.  The  double-armed  levers  D  D 
work  loosely  on  the  hubs  of  the  steam  bonnets ;  they  are  con- 
nected to  the  wrist-plate  B  by  the  rods  K  K,  the  levers  M  M  are 
keyed  to  the  valve  stems  J  J",  and  are  also  connected  by  the  rods 
0  0  to  the  dash  pots  P  P.  The  double-armed  levers  D  carry  at 
their  outer  ends  what  are  called  steam  hooks,  F  F,  these  being  pro- 
vided with  hardened  steel  catch  plates,  which  engage  with  arms 
'  M  Jf,  making  the  arm  Jtf  and  the  hook  F  work  in  unison  until 
steam  is  to  be  cut  off.  At  this  point  another  set  of  levers  or  cams 
G  6r,  which  are  connected  by  the  cam  rods  H  H,  to  the  governor, 
come  into  play,  causing  the  catch  plates  on  the  hooks  F  to  release 
the  arms  MM.  the  outer  ends  of  which  are  then  pulled  downwards 
by  the  dash-pot  plunger,  causing  the  steam  valves  to  rotate  on 
their  axis  and  thus  cut  off  steam.  These  are  the  essential  fea- 
tures of  the  Corliss  gear. 

The  exhaust  valve  arms  N  are  connected  to  the  wrist-plate  by 
the  rods  L  L,  and  it  is  seen  that  all  the  valves  receive  their 
motion  from  the  wrist-plate  B;  the  latter  receives  its  motion 
from  the  hook-rod  A;  this  rod  is  generally  attached  to 
a  rocker  arm  not  shown ;  to  this  arm  the  eccentric  rod  is 


HANDBOOK    ON    ENGINEERING 


209 


H 


210 


HANDBOOK    ON    ENGINEERING. 


also  attached.  The  rocker  arm  is  usually  placed  about  mid- 
way between  the  wrist-plate  and  eccentric,  and  in  the  center 
of  its  travel  stands  in  a  vertical  position. 

The  setting  of  the  valves  is  not  a  difficult  matter,  when,  on 
the  wrist-plate,  its  support,  valves  and  cylinder,  the  customar/ 
marks  have  been  placed  for  finding  the  relative  positions  of 
wrist-plate  and  valves. 


G- 


Fig.  4. 

Now,  referring  to  Fig.  4,  when  the  back  bonnets  of  the  valve 
chambers  have  been  taken  off,  there  will  generally  be  found  a  mark 
or  line,  r,  on  the  end  of  each  steam  valve  s  s,  coinciding  with  the 
working  or  opening  edge  of  each  valve  ;  another  line,  £,  will  be 
found  on  each  face  of  the  steam  valve  chamber  coinciding  with 
the  working  edge  of  the  steam  port.  The  exhaust  valves  and 
their  chambers  are  marked  in  a  similar  way,  i.  e.,  the  line  u  on 
the  end  of  each  exhaust  valve  coincides  with  the  working  edge  of 
the  valve,  and  the  line  a;,  on  the  face  of  ^ach  exhaust  valve 


HANDBOOK    ON    ENGINEERING.  211 

chamber,  coincides  with  the  working  edge  of  the  exhaust  port. 
On  the  hub  of  the  wrist  plate  will  be  found  three  lines  n,  c,  n, 
placed  in  such  a  way  that  when  the  line  c  coincides  with  the 
line  b  on  wrist  plate,  the  wrist  plate  will  stand  exactly  in  the 
center  of  its  motion,  and  when  the  line  b  coincides  with  either 
of  the  lines  n,  n,  the  wrist  plate  will  be  at  one  of  the  extreme 
ends  v  or  w  of  its  travel. 

In  setting  the  valves,  the  first  step  will  be  to  set  the  wrist- 
plate  in  its  central  position,  so  that  the  lines  b  and  c  will  coin- 
cide, and  fasten  the  wrist-plate  in  this  position  by  placing  a 
piece  of  paper  between  it  and  the  washer  R  on  its  supporting 
pin.  Now  set  the  steam  valves  so  that  they  will  have  a  slight 
amount  of  lap,  that  is  to  say,  the  lines  r,  r,  must  have  moved  a 
little  beyond  the  lines  £,  t.  The  amount  of  this  lap  depends 
much  on  individual  preference  and  experience ;  it  ranges  from 
A  to  J  ^or  sma^  engines,  and  from  J-  to  |  inch  for  compara- 
tively large  engines.  This  lap  is  obtained  by  lengthening  or 
shortening  the  rods  TTTTby  means  of  the  adjusting  nuts. 

Now  place  the  exhaust  valves  e,  e,  by  lengthening  or  shorten- 
ing the  rods  L  L  by  means  of  the  adjusting  nuts,  in  a  position 
so  that  the  working  edges  will  just  open  the  exhaust  ports,  or, 
in  other  words,  place  the  lines  u  and  x  in  line  with  each  other 
as  indicated  in  illustration. 

The  next  step  will  be  to  adjust  the  rocker  arm.  Set  this  arm 
in  a  vertical  position  by  means  of  a  plumb  line,  and  connect  the 
eccentric  rod  to  it ;  then  turn  the  eccentric  around  on  the  shaft, 
and  see  that  the  extreme  points  of  travel  are  at  equal  distances 
from  the  plumb  line.  To  secure  this  a  little  adjustment  in  the 
stub  end  of  the  eccentric  rod  may  be  necessary.  Now  connect  the 
hook  rod  A  to  the  wrist- plate.  The  paper  between  the  wrist- 
plate  and  the  washer  on  the  supporting  pin  should  now  be  taken 
out,  so  that  the  wrist-plate  which  is  connected  to  the  valves  can 
be  swung  on  its  pin.  Now  turn  the  eccentric  around  on  the  shaft 


212  HANDBOOK    ON   ENGINEERING. 

in  order  to  determine  the  extreme  points  of  travel  of  the  wrist- 
plate.  If  all  parts  have  been  correctly  adjusted,  the  line  b  will 
coincide  with  the  lines  ??,  n,  at  the  extreme  points  of  travel ;  if 
this  is  not  the  case,  the  hook  rod  will  have  to  be  adjusted  at  its 
stub  end  so  as  to  obtain  the  desired  equalized  motion  of  tbe 
wrist-plate. 

The  next  step  will  be  to  set  the  valves  correctly  with  reference 
to  the  position  of  the  crank ;  to  do  this  the  length  of  the  rods  A", 
K,  L,  and  L  must  not  be  changed,  but  the  following  mode  of 
procedure  should  be  followed  :  Place  the  crank  on  one  of  its  dead 
centers  (see  page  195)  and  turn  the  eccentric  loosely  on  the  shaft 
in  the  direction  in  which  the  engine  is  to  run,  until  the  steam 
valve  nearest  to  the  piston  shows  an  opening  or  lead  of  ^  to  ^ 
inch.  After  the  proper  lead  has  been  given  to  this  valve,  secure 
the  eccentric,  and  turn  the  shaft  with  eccentric  in  the  same  direc- 
tion in  which  the  engine  is  to  run  until  the  crank  is  on  the  oppo- 
site dead  center,  and  notice  if  the  opening  or  lead  at  this  end  of 
the  cylinder  is  the  same  as  on  the  other  steam  valve ;  if  not, 
shorten  or  lengthen  slightly,  as  may  appear  necessary,  the  con- 
nection between  the  wrist-plate  and  eccentric.  Of  course  much 
adjustment  in  the  length  of  these  connections  is  not  admissible 
without  resetting  the  valves  with  reference  to  the  wrist-plate.  The 
compression  on  an  engine  is  a  very  important  factor,  upon  which 
cool  and  quiet  running  depends.  With  exhaust  valves  line  and 
line  about  5  per  cent  compression  is  secured,  which  is  equal  to  1 J' 
for  36"  stroke  and  2"  for  42"  stroke.  In  case  more  compression 
is  desired,  the  exhaust  valves  must  be  given  a  little  lap. 

To  set  the  exhaust  valves  for  a  given  compression,  say,  2 
inches,  first  measure  off  2  inches  from  the  ends  of  the  cross- head 
travel  as  shown  in  Fig.  5  (not  from  the  ends  of  the  guide). 
Then  turn  the  crank  in  the  direction  it  is  to  run  until  the  end  of 
the  crosshead  reaches  the  line  on  the  guide.  Adjust  the  exhaust 
valve  corresponding  to  this  end  of  the  stroke  so  that  it  just  closes 


HANDBOOK    ON    ENGINEERING. 


213 


the  port.  Turn  the  crank  over  the  center  and  back  on  the  return 
stroke  until  the  opposite  end  of  the  cross-head  reaches  the  line  on 
the  opposite  end  (to  the  first  mark)  of  the  guide.  Then  adjust 
the  exhaust  valve  corresponding  to  this  end  of  the  stroke  so  that 
it  just  closes  the  port.  Both  exhaust  valves  will  then  close  the 
ports  when  the  piston  reaches  a  point  2  inches  from  the  working 
end  of  the  guide  and  the  engine  will  then  have  exactly  2  inches 


Fig.  5. 

compression.  If  this  is  found  to  be  too  much  or  too  little,  as 
determined  by  the  running  qualities  of  the  engine,  it  may  be 
varied  either  way  by  adjusting  the  length  of  the  rods  L  and  L, 
being  careful  to  turn  each  nut  exactly  the  same  amount. 

The  only  thing  which  remains  now  to  be  done  is  to  adjust  the 
cam  rods  H,  //,  to  produce  an  equal  cut-off  at  each  end  of  the 
cylinder.  On  the  column  of  most  Corliss  engine  governors  will 
be  found  a  stop  device,  sometimes  in  the  form  of  a  loose  pin, 
some  form  of  cam  motion  or  movable  collar.  This  device  is  for 
the  purpose  of  preventing  the  governor  from  reaching  its  lowest 
position,  for  when  it  reaches  the  latter  position  the  valves  should 
not  hook  on.  Should  the  governor  belt  break  or  become  iiieffect- 


214  HANDBOOK    ON    ENGINEERING. 

ive,  the  governor  will  stop  and  reach  its  lowest  position  on  the 
column,  thereby  bringing  the  safety  cam  Y  in  underneath  the 
inner  member  of  the  hook  F  which  prevents  the  latter  from 
engaging  arm  M,  and  as  the  valves  cannot  hook  on  when  it  is  in 
this  position  the  admission  of  steam  to  the  cylinder  is  entirely 
shut  off  and  the  engine  will  come  to  a  standstill. 

It  will  be  apparent  that  the  stop  on  the  governor  column  should 
be  removed  or  otherwise  rendered  inoperative  as  soon  as  the 
engine  has  attained  full  speed,  and  should  again  be  placed  in 
active  position  when  stopping  the  engine  in  the  usual  way.  As 
the  stop  just  mentioned  determines  the  lowest  position  of  the 
governor  at  which  the  valves  should  hook  up,  it  should  be  kept 
in  place  while  the  foregoing  adjustments  are  being  made. 

Next,  unhook  the  reach  rod  from  the  wrist  plate  and  by  means 
of  the  starting  bar  move  the  wrist  plate  over  until  the  lines  b  and 
n  are  nearly  opposite  each  other.  The  head  end  valve  should 
now  have  opened  the'  port  to  nearly  the  limit,  which  may  be 
ascertained  by  the  marks  on  the  ends  of  the  valve.  Now,  adjust 
the  governor  rod  H  so  that  the  projection  or  cam  on  the  disk  G 
operated  by  the  governor  will  come  in  contact  with  the  inner 
member  of  the  steam  hook  F,  so  that  the  valve  will  be  tripped  or 
released  when  the  marks  b  and  n  are  exactly  in  line.  As  all 
governors  do  not  move  an  equal  amount  to  produce  a  given 
change  in  the  point  of  cut-off,  it  will  be  safer  to  hook  the  reach 
rod  on  the  wrist-plate  and  have  the  engine  turned  in  the  direction 
in  which  it  is  to  run,  until  the  head  end  valve  is  released,  than  to 
adjust  the  cut-off  with  the  use  of  the  starting  bar  only.  To 
prove  the  correctness  of  the  cut-off  adjustment,  raise  the  gover- 
nor balls  to  a  position  where  they  probably  would  be  when  at 
work  and  block  them  there ;  then,  with  the  connections  made 
between  the  eccentric  and  the  wrist-plate,  turn  the  engine  shaft 
slowly  in  the  direction  in  which  it  is  to  run,  and  when  the 
valve  is  released,  measure  upon  the  slide  the  distance  which 


HANDBOOK    ON    ENGINEERING. 


215 


the  crosshead  has  moved  from  its  extreme  position.  Continue  to 
turn  the  shaft  in  the  same  direction,  and,  when  the  other  valve  is 
released,  measure  the  distance  through  which  the  crosshead  has 
moved  from  its  extreme  position,  and  if  the  cut-off  is  equalized, 
these  two  distances  will  be  equal  to  each  other.  If  they  are  not, 
adj  ust  the  length  of  the  cam  rods  until  the  points  of  cut-off  are 
equal  distances  from  the  beginning  of  the  stroke.  Replace  the 
back  bonnets  and  see  that  all  connections  have  been  properly 
made,  which  will  complete  the  setting  of  the  valves. 


Fig.  6, 


ADJUSTMENT  WITH  TWO  ECCENTRICS. 

In  order  to  obtain  a  greater  range  of  cut-off  in  Corliss  engines 
a  separate  steam  and  exhaust  eccentric  is  used.  With  two  eccen- 
trics the  admission  and  exhaust  valves  can  be  adjusted  independ- 
ently, and  steam  may  be  cut  off  anywhere,  nearly  to  the  end  of 
the  stroke. 

The  work  of  setting  the  valves  of  a  Corliss  engine  having  two 


216 


HANDBOOK   ON   EXGI MAKING. 


HANDBOOK    ON    ENGINEERING.  217 

eccentrics  is  not  particularly  complicated  as  many  engineers  seem 
to  think.  After  inspecting  the  type  of  releasing  gear  employed 
and  knowing  in  which  direction  the  engine  is  to  run,  finding  the 
direction  in  which  to  turn  the  eccentric  becomes  a  very  simple 
matter.  When  setting  the  steam  valves  we  have  one  eccentric  to 
turn  as  in  the  case  of  the  single  eccentric  engine,  and  when  set- 
ting the  exhaust  valves  another  eccentric  must  be  turned,  but  this 
does  not  add  complication  to  the  work,  although  it  requires  a 
little  more  time.  The  work  of  centralizing  the  positions  of  the 
various  parts,  equalizing  the  movements  and  setting  and  adjust- 
ing the  valve  gear  is  practically  the  same  as  with  the  single  eccen- 
tric engine.  Set  the  wrist-plate  central  as  shown  in  Fig.  6,  and 
adjust  the  valve  rods  ;  but  in  this  case  the  steam  valves  are  set 
with  negative  lap  which  is  usually  a  little  less  than  half  the 
port  opening.  The  first  step  is  to  set  the  exhaust  eccentric 
(as  it  is  generally  placed  next  to  the  bearing).  To  do  this 
turn  the  engine  until  the  piston  is  in  the  position  shown 
in  Fig.  7,  so  as  to  obtain  a  compression  of  about  5 
per  cent  of  the  stroke.  Then  turn  the  exhaust  eccentric 
loosely  on  the  shaft  in  the  direction  the  engine  is  to  run,  until  the 
exhaust  valves  are  line  and  line.  Then  secure  the  eccentric  and 
turn  the  engine  on  the  other  end  in  the  same  position  to  prove 
the  correctness  of  the  other  exhaust  valve. 

The  next  step  is  to  set  the  steam  eccentric ;  place  the  crank 
on  either  one  of  its  dead  centers,  then  turn  the  steam  eccentric 
loosely  on  the  shaft  until  the  steam  valve  on  the  same  end  the 
piston  is,  has  the  required  opening  or  lead,  which  varies  from  -^" 

to  Ty. 

These  directions  apply  to  engines  in  which  the  reach  rod  from 
the  eccentric  is  connected  to  the  wrist-plate  above  the  center 
pin  /£,  Fig.  No.%3.  When  the  reach  rod  is  connected  to  wrist- 
plate  below  the  pin  /£,  the  eccentric  should  be  turned  the  opposite 
direction  to  that  in  which  the  engine  is  to  run. 


218 


HANDBOOK   ON   ENGINEERING. 


HANDBOOK    ON    ENGINEERING. 


219 


The  arrangement  of  the  steam  rods  in  Fig.  3  is  in  every  re- 
spect satisfactory  in  connection  with  a  single  eccentric  valve  gear, 
for  in  that  case  a  slow  initial  valve  motion  is  imperative,  and  it  is 
obtained  by  the  lateral  movement  of  the  radius  rod.  But  with 
two  eccentrics  quicker  initial  motion  is  feasible  and  desirable,  and 
it  is  obtained  by  reversing  the  valve  motion  as  in  Fig.  6.  Sepa- 
rate eccentrics  require  separate  wrist-plates,  which  are  usually 
placed  on  the  same  pin. 


Fig.  9. 

Figs*  8  and  9  show  how  the  eccentrics  may  be  placed  on  the 
shaft.  The  steam  eccentric  is  at  point  4,  Fig.  8,  the  exhaust 
eccentric  is  at  point  1,  Fig.  9,  and  the  crank  is  at  its  dead  center 
at  G.  Individual  eccentric  circles  are  shown  for  the  sake  of  clear- 
ness. An  imaginary  motion  of  the  eccentric  will  point  out  the 
various  events.  Referring  to  Fig.  8,  near  point  2,  at  the  end  of 


220 


HANDBOOK    ON    ENGINEERING. 


the  throw,  the  hook  connects  with  the  steam  valve  ;  at  point  3 
the  steam  edges  are  at  the  point  of  separating  and  the  eccen- 
tric motion  2-3  determines  the  initial  valve  motion.  When  the 
eccentric  is  at  point  4  the  crank  is  at  its  dead  center  as 
shown.  At  point  5  the  steam  wrist-plate  is  in  its  central  position 
and  in  that  position  the  valve  does  not  cover  the  port,  as  with 
the  single  eccentric  gear,  but  the  port  is  open  to  a  certain  extent, 
determined  by  the  eccentric  motion  3-5.  Point  7  marks  the  end 


Fig.  10. 

of  the  throw,  and  the  corresponding  position  of  the  crank  is  at  Cl 
at  about  three-quarters  of  the  piston  stroke,  and  the  limit  of  cut- 
off is  a  little  later.  If  the  hook  does  not  strike  the  knock- 
off  cam  the  valve  will  remain  open  until  closed  by  the  return 
stroke  of  the  eccentric  at  point  9,  near  the  middle'  of  the 
return  piston  stroke.  The  exhaust  action  is  discernible,  Fig.  8. 


HANDBOOK   ON    ENGINEERING. 


221 


It  is  similar  to  the  single  eccentric  action,  bat  with  this  differ- 
ence, that  the  release  at  point  5  occurs  at  about  95  per  cent  of 
the  stroke,  and  the  exhaust  is  also  cut  off  at  about  95  per  cent 
of  the  return  stroke  at  point  8. 

The  motion  of  the  exhaust  valve  after  it  has  closed  the  port  is 
determined  by  the  eccentric  motion  8-2-^5,  and  full  period  of 
exhaust  opening  is  obtained  by  the  eccentric  motion  5-7-8.  In 
case  the  exhaust  valve  motion  is  designed  and  set  with  lap,  Fig. 
10  shows  the  effect  lap  has  on  the  exhaust  valves.  The  lap  when 
wrist-plate  is  central  is  determined  by  motion  A-B.  It  will  be 


Fig.   11. 

noticed  that  the  compression  begins  at  A  at  about  90  per  cent  of 
the  stroke,  and  the  release  at  E  occurs  at  98  per  cent  of  the 
return  stroke  and  the  exhaust  opening  E,  (7,  A,  is  shortened. 
Where  lap  is  used  on  the  exhaust  valve  it  has  the  effect  of  making 
earlier  compression  and  later  release.  A  valve  gear  designed  to 
be  operated  by  a  single  eccentric  cannot  very  well  be  made  to  cut 
off  much  later  than  at  half  stroke,  even  when  a  separate  exhaust 
eccentric  is  added.  For  the  slow  initial  valve  motion  requires  at 
least  half  the  throw  of  the  eccentric,  and  the  other  half  is  not 
sufficient  for  a  late  cut-off,  and  it  will  readily  be  seen  from  an 
inspection  of  Figs.  4  and  6,  that  a  quicker  initial  valve  motion  in 


222  HANDBOOK    ON    ENGINEERING. 

Fig.  4  would  involve  radical  changes  in  the  valve  gear.  However, 
the  range  of  cut-off  may  be  extended  by  moving  the  eccentric 
back,  sacrificing  the  lead,  and  to  this  there  is  no  objections  when 
it  does  not  involve  later  release.  The  advantage  gained  by  a 
second  eccentric  would  consist  in  more  compression  and  earlier 
release.  After  setting  the  valves  and  making  the  final  adjustment, 
if  it  is  convenient  an  indicator  should  be  applied  to  the  engine 
when  at  work  to  verify  the  adjustment  of  the  valves  for  the  best 
possible  conditions  for"economical  operation. 

Fig.  10  indicates  position  of  eccentric  at  J  cut  off  which  can 
be  extended  some  by  giving  the  steam  valves  a  little  more  nega- 
tive lap,  but  as  this  shortens  the  amount  of  lap  when  closed,  it 
may  cause  leakage  in  the  steam  valves. 

COMPOUND   ENGINE. 

The  compound  engine  is  practically  two  single  engines  con- 
nected together  and  so  arranged  that  the  exhaust  steam  from 
one  engine  passes  into  and  becomes  the  "  live  "  steam  for  the 
other,  in  other  words  the  first,  or  high  pressure  cylinder  receives 
its  supply  of  steam  from  the  boiler  and  the  second  or  low 
pressure  cylinder  receives  its  supply  from  the  high  pressure 
cylinder.  The  object  of  the  compound  engine  is  to  enable  the 
steam  to  expand  to  the  lowest  possible  pressure  with  the  least 
loss  by  condensation.  When  steam  expands  its  temperature 
decreases,  so  that  by  the  time  the  piston  reaches  the  end  of  the 
stroke  the  temperature  of  the  steam  and  consequently  the  tem- 
perature of  the  cylinder  walls  is  considerably  below  the  temper- 
ature of  the  incoming  steam.  The  fresh  steam  of  hight  empera- 
ture  coming  from  the  boiler  comes  in  contact  with  the  walls  of 
the  cylinder  which  have  been  cooled  to  the  temperature  of  the 
exhaust  steam,  and  the  result  is  a  considerable  portion  of  the 
fresh  steam  is  condensed,  the  latent  heat  serving  to  reheat  the 


HANDBOOK    ON    ENGINEERING 


223 


224  HANDBOOK    ON    ENGINEERING. 

cylinder  walls.  It  will  be  understood  that  were  it  possible  to 
keep  the  cylinder  at  a  higher  temperature,  less  steam  would  be 
condensed  in  warming  it  at  each  stroke  and  consequently  more 
steam  would  be  available  for  useful  work.  In  the  compound 
engine  the  steam  is  expanded  partly  in  one  cylinder  and  partly 
in  the  other  so  that  the  difference  between  the  temperatures  of  the 
incoming  and  exhaust  steam  in  each  cylinder  is  greatly  reduced. 
By  this  means  steam  may  be  expanded  from  a  given  initial  pres- 
sure to  a  given  final  pressure  with  a  loss  of  nearly  twenty-five 
per  cent  less  than  would  be  incurred  were  the  same  expansion  to 
take  place  in  a  single  cylinder.  It  is  due  principally  to  avoiding 
the  loss  by  cylinder  condensation  that  the  compound  engine, 
considered  as  a  type  of  engine,  can  perform  nearly  twenty-five 
per  cent  more  work  with  the  same  weight  of  steam  than  can  be 
obtained  when  the  steam  is  expanded  in  one  cylinder  only. 

In  order  to  utilize  the  low  pressure  steam  escaping  from  the 
high  pressure  cylinder  it  is  necessary  to  provide  a  larger  area 
of  piston  so  that  the  low  pressure  steam  acting  on  a  large  sur- 
face will  do  as  much  work  as  the  high  pressure  steam  acting  on  a 
smaller  area.  It  is  for  this  reason  that  the  low  pressure  cylinder 
of  compound  engines  is  always  made  larger  than  the  high  pressure 
cylinder.  The  required  size  of  low  pressure  cylinder  for  a  given' 
size  of  high  pressure,  depends  upon  the  number  of  times  the 
steam  is  to  be  expanded,  the  initial  steam  pressure  and  the  nature 
of  the  work  the  engine  is  intended  for.  For  steady  loads  the 
difference  in  the  size  of  the  two  cylinders  may  be  greater  than 
where  the  load  is  constantly  changing  between  wide  limits  as 
nearly  always  occurs  in  street  railway  service. 

Compound  engines,  as  this  term  is  generally  employed,  are 
built  of  two  types,  the  tandem  compound,  Fig.  1,  and  the  cross 
compound,  Fig.  2.  In  the  tandem  compound  the  work  of  both 
pistons  is  transmitted  to  the  crank  through  one  piston  rod,  cross- 
head  and  connecting  rod,  while  in  the  cross  compound  there  are 


HANDBOOK    OX    ENGINEERING 


225 


226  HANDBOOK    ON    ENGINEERING. 

two  complete  engines  placed  side  by  side,  the  cranks  of  which 
are  generally  set  90  degrees  apart.  It  will  be  seen  that  in  the 
tandem  compound  engine  it  makes  but  little  difference  from  the 
mechanical  standpoint  whether  the  work  is  divided  evenly  between 
the  two  cylinders  or  not  because  both  pistons  move  in  unison 
and  drive  the  same  crank.  In  the  cross  compound  engine  it  is 
necessary,  in  order  to  secure  a  uniform  turning  effort  at  the 
shaft,  to  have  the  work  divided  as  nearly  equally  between  the 
two  cylinders  as  the  conditions  will  permit.  In  the  tandem  com- 
pound engine  the  principal  consideration  is  the  proper  working 
of  the  steam,  and  the  sizes  of  the  cylinders  are  determined  by 
the  number  of  expansions  to  be  effected  in  both  cylinders,  or 
the  total  number  of  expansions,  as  it  is  called,  and  the  initial 
pressure.  As  the  equal  division  of  the  work  between  the  two 
cylinders  in  compound  engines  is  essential,  the  ratio  of  the  cylin- 
ders is  generally  for  noncondensing  21  to  1  for  100  Ibs.,  2J  to  1 
for  125  Ibs.,  and  3  to  1  for  150  Ibs.  initial  pressure,  and  for  con- 
densing 3  to  1  for  100  Ibs.,  3J  to  1  for  125  Ibs.,  and  4  to  1  for 
150  Ibs.,  initial  pressure. 

The  number  of  expansions  required  in  a  compound  engine  is 
represented  by  the  quotient  of  the  absolute  initial  pressure  divided 
by  the  absolute  terminal  pressure.  If  steam  is  to  be  used  at  105 
pounds  gauge  pressure  and  is  to  be  expanded  down  to  10  pounds 

105  +  15 
absolute  in  the  low  pressure  cylinder,  there  will  be r^ =  12 

expansions.  A  simple  rule  for  finding  the  ratio  of  the  area  of 
cylinders  for  noncondensing,  is  to  divide  the  absolute  initial  pres- 
sure by  the  terminal  pressure  which  equals  the  expansions  in  both 
cylinders  and  the  square  root  of  total  expansions  equals  the  ratio 
of  cylinders. 

For  example :  150  Ibs.  initial  pressure  plus  15  Ibs.  equals  165 
Ibs.  absolute  initial  pressure  divided  by  16  Ibs.  terminal  pressure 
equals  10.3  total  expansions,  and  the  square  root  of  10.3  equals 


HANDBOOK    ON    ENGINEERING.  227 

3.2  equals  ratio  of  cylinders.  Care  should  be  taken  in  non- 
condensing  engines  so  that  the  ratio  of  the  low  pressure  cylinder 
is  not  too  large,  as  in  such  cases  the  steam  in  low  pressure  cylin- 
der would  expand  to  less  than  the  atmospheric  pressure,  and 
thus  make  loops  on  indicator  card,  which  would  incur  a  serious 
loss. 

The  calculation  of  the  diameters  of  cylinders  for  a  compound 
condensing  engine  when  the  data  are  given,  follows.  Take  an 
engine  that  is  to  develop  500  horse  power  with  an  initial  pressure 
of  105  pounds  gauge,  or  120  pounds  absolute,  the  steam  to  be 
expanded  to  a  terminal  pressure  of  6  pounds  absolute.  The  total 
expansion  of  steam  in  both  cylinders  is  120  -f-  6  =20. 

Expansion  in  each  cylinder  =  -^20=4.  47. 

Point  of  cut-off  in  each  cylinder,  per  cent  of  stroke  —  — 

4.47 

22.3  per  cent,  1  -|-  hyp.  log.  of  expansion  in  each  cylinder  =  1  -j- 
hyp.  log.  4.47  =  2.497. 

Terminal  and  back  pressure  in  high  pressure  cylinder,  and  the 

120 
initial  pressure  in  the  low  =  j^p  =  26.8  pounds. 

Mean  effective  pressure  in  h.  p.  cyl.  =  26.8  X  2.497  —  26.8 
=  40.11  pounds. 

Mean  effective  pressure  in  1.  p.  cyl.  (assuming  3  Ibs.  back 
press.)  =  6  X  2.497  —  3  =  11.98  pounds. 

If  half  the  work  is  to  be  done  in  each  cylinder,  which  is  de- 
sirable in  cross  compound  engines,  each  cylinder  must  do  250 
horse  power  of  work.  Assuming  the  piston  speed  to  be  600  feet 
per  minute,  the  area  of  the  low  pressure  cylinder  is 

33000  X  H.  P.  33,000  X  250 

Piston  speed~X~effective  P*es7.  ™  600  X  H-98  =  'U7'  7  sc*uare 
inches  =  38  ins.  diameter. 


QO  nnrj  \/ 
Area  of  high  pressure  cylinder  by  same  rule  is  :  —  !  _ 

600X40.11 

=  342.3  square  inches  =  21  inches  diameter. 


228 


HANDBOOK    ON    ENGINEERING. 


Ratio  of  cyl.  = 


40.11 
11.98 


=  3.3  to  one. 


The  clearance  and  the  areas  of  the  piston  rods  have  not  been 
taken  account  of  by  separate  processes  in  the  foregoing  calcu- 
lations. These  should  always  be  included  when  making  calcu- 
lations involving  the  pressure  and  expansion  of  steam  in  engine 
cylinders.  The  method  of  finding  the  number  of  expansions 
taking  place  in  a  compound  engine  may  be  readily  -understood 
by  referring  to  the  diagram,  Fig.  3.  The  shaded  area  in  the 


/  Vol.     £  Vo/s, 


Fig.  3. 

smaller  cylinder  represents  the  initial  volume  of  steam  in  the 
high  pressure  cylinder,  that  is  to  say,  this  represents  the  volume 
of  steam  taken  from  the  boiler  for  one  stroke,  or  during  one-half 
revolution.  The  point  of  cut-off  is  at  one-third  stroke  and  the 
area  of  the  low  pressure  cylinder  is  three  times  that  of  the  high 
pressure  cylinder.  It  will  be  seen  that  when  the  low  pressure 
piston  moves  to  one-third  stroke  the  volume  of  the  cylinder  V 
behind  the  piston  is  equal  to  the  volume  of  the  entire  high  pres- 
sure cylinder.  This  shows  that  the  capacity  or  contents  of  the  low 
pressure  cylinder  is  three  times  that  of  the  high  so  that  for  every 


HANDBOOK    ON   ENGINEERING. 


229 


volume  of  steam  and  therefore  for  every  expansion  taking  place  in 
the  high  pressure  cylinder  there  will  be  three  volumes,  and  three 
expansions  taking  place  in  the  low  pressure  cylinder.  This 
shows  why  the  total  number  of  expansions  in  a  compound  engine 
is  the  number  in  the  high  pressure  cylinder  multiplied  by  the 
number  in  the  low  pressure  cylinder.  In  the  diagram,  Fig.  8, 
when  the  small  piston  reaches  the  end  of  the  stroke  the  steam 
will  have  expanded  three  times,  that  is,  it  will  occupy  three  times 
the  space  it  did  at  the  point  of  cut-off.  Now  when  the  large 
piston  reaches  the  end  of  the  stroke  each  of  the  three  volumes  a, 
a  and  a,  Fig.  4,  will  have  been  expanded  three  more  times  and 
the  total  will  be  3X3=9  expansions,  that  is,  the  original 
volume  a,  Fig.  o,  will  then  occupy  nine  times  the  space  it  did  when 


& 


0* 


Fig.  4. 

first  let  into  the  high  pressure  cylinder.  To  find  the  number  of 
expansions  in  a  compound  engine  multiply  the  number  of  expan- 
sions in  the  high  pressure  cylinder  by  the  number  in  the  low,  or 
multiply  the  number  of  expansions  in  the  high  pressure  cylinder 
by  the  ratio  of  cylinder  areas ;  the  product  will  be  the  number 
required. 

Again  referring  to  Fig.  4,  it  will  be  seen  that  the  low  pressure 
cylinder  must  receive  a  high-pressure  cylinderful  of  steam  at  each 


230  HANDBOOK    ON    ENGINEERING. 

stroke  otherwise  the  pressure  in  the  receiver  and  the  back  pressure 
on  the  high  pressure  piston  will  rise  too  high  and  a  loss  of  power 
will  result,  or  if  the  pressure  be  too  low  in  the  larger  cylinder  the 
small  piston  will  drive  the  larger  one  which  will  again  result  in 
loss  of  power.  It  has  been  shown  that  the  volume  of  both 
cylinders  vary  in  proportion  to  the  areas,  that  is,  if  the  areas  are 
as  1  to  3  then  when  both  pistons  have  reached,  say,  one-third 
stroke  the  volume  of  one  will  be  3  times  the  volume  of  the  other, 
and  when  the  larger  piston  in  this  case  travels  one-third  of  the 
stroke  the  capacity  of  the  low  pressure  cylinder  behind  the  piston 
will  then  be  equal  to  the  whole  of  the  smaller  cylinder  and  will  be 
capable  of  containing  all  the  steam  used  during  a  full  stroke  of 
the  smaller  piston,  or  a  high-pressure  cylinderful  of  steam.  This 
steam  then  expands  during  the  remaining  two- thirds  of  the  stroke. 
Now  it  will  be  readily  understood  that  if  a  cut-off  valve  were  pro- 


Hls\  Pressure  Diaeram. 
X 


lev  Preuurt  Diaoram. 
^7+snos.    2/*r&  . 


Fig.  6. 

vided  on  the  low  pressure  cylinder  and  is  set  to  cut  off  at  less  than 
one-third  stroke  (with  a  ratio  of  cylinder  areas  1  to  3)  the  low 
pressure  cylinder  will  not  take  a  high  pressure  cylinderful  of 
steam  when  steam  is  cut  off,  and  the  pressure  in  the  receiver  must 
necessarily  rise.  Reducing  the  volume  of  steam  entering  the  low 
pressure  cylinder  apparently  tends  to  lessen  the  work  done  by  the 
larger  piston  and  consequently  more  work  must  apparently  be 


HANDBOOK    ON    ENGINEERING.  231 

done  by  the  high  pressure  piston.  This  in  turn  causes  a  later 
cut-off  in  the  small  cylinder  as  shown  in  Fig.  5,  dotted  lines, 
which  serves  to  neutralize  the  effect  of  the  higher  back  pressure 
so  that  while  the  cut-off  has  been  made  later,  the  mean  effective 
pressure  remains  practically  the  same.  The  higher  backpressure 
on  the  small  piston  means  a  higher  initial  pressure  in  the  low 
pressure  cylinder,  see  Fig.  6  dotted  lines,  which  causes  more 
power  to  be  developed  in  the  latter  cylinder.  Thus  it  is  seen 
that,  within  certain  limits,  shortening  the  cut-off  in  the  low  pres- 
sure cylinder  puts  more  of  the  load  upon  the  low  pressure  piston. 

On  the  other  hand  when  the  low  pressure  piston  is  doing  more 
work  than  the  high  pressure,  the  cut-off  in  the  low  pressure 
cylinder  may  be  lengthened.  This  permits  the  low  pressure 
cylinder  taking  more  steam  and  consequently  the  receiver  pressure 
and  the  back  pressure  on  the  high  pressure  piston  are  reduced 
and  the  work  done  by  the  high  pressure  piston  is  thus  increased. 
By  manipulating  the  cut-off  on  the  low  pressure  cylinder  the  load 
on  the  two  pistons  may  be  equalized  or  very  nearly  so  except 
when  the  engine  is  considerably  underloaded  or  overloaded.  The 
range  of  maximum  economy  is  not  as  great  with  the  compound  as 
with  the  simple  engine,  that  is  to  say,  the  load  may  be  varied 
more  widely  from  the  point  where  the  best  economy  is  obtained, 
in  the  simple  engine  than  in  the  compound  which  is  due  to  the 
large  difference  in  cylinder  areas  in  the  latter  engine.  At  very 
early  cut-off  both  the  high  pressure  and  the  low  pressure  cylinders 
work  the  steam  very  similarly  to  the  simple  engine  and  as  the  loss 
by  cylinder  condensation  increases  with  an  increase  in  the  range 
of  temperatures  it  follows  that  an  underloaded  compound  engine 
is  but  little  if  any  more  economical  than  a  simple  engine  working 
with  a  similar  initial  point  of  cut-off. 

In  compound  automatic  cut-off  engines  the  point  of  cut-off  will 
be  nominally  the  sa*me  in  both  cylinders,  we  say  nominally  (in 
name  only)  because  the  initial  pressure  and  the  extent  of  the 


232  HANDBOOK   ON   ENGINEERING. 

vacuum  have  some  influence  upon  the  receiver  pressure  and  the 
mean  effective  pressure  in  the  low  pressure  cylinder.  In  most 
compound  engines  in  which  the  cut-off  mechanism  of  both  cylin- 
ders are  operated  by  a  single  governor,  provision  is  made  for 
adjusting  the  cut-off  of  the  low  pressure  cylinder  relative  to  that 
in  the  high,  so  that  while  the  nominal  cut-off  may  be,  say,  one- 
fourth  stroke,  the  actual  points  of  cut-off  maybe  one-fourth  in  the 
high  pressure  and  -£•$  in  the  low  pressure  cylinder,  the  governor, 
however,  varying  both  points  of  cut-off  as  the  load  changes. 

HORSE  POWER  OF  COMPOUND  ENGINE. 

Little  can  be  done  in  finding  the  horse  power  of  compound  en- 
gines without  the  indicator  because  of  the  uncertainty  of  the  points 
of  cut-off  and  consequently  of  the  back  pressure  and  mean  effec- 
tive pressures.  The  mean  effective  pressure  in  each  cylinder  may 
be  computed  by  using  assumed  data,  by  the  same  rules  given 
for  simple  engines,  but  it  will  readily  be  understood  that  assumed 
data  furnishes  assumed  results  only.  Knowing  the  mean  effective 
pressure  areas  and  speed  of  the  pistons  the  horse  power  of  a 
compound  engine  is  found  as  follows:  Multiply  the  areas  of 
the  high  pressure  piston  by  its  mean  effective  pressure  and 
divide  by  the  area  of  the  low  pressure  piston,  then  add  this  quotient 
to  the  mean  effective  pressure  in  the  low  pressure  cylinder.* 
Call  this  answer  1.  Multiply  the  area  of  the  low  pressure 
piston  by  the  piston  speed  in  feet  per  minute  and  by  answer  1, 
and  divide  the  last  product  by  33,000  ;  the  quotient  will  be 
the  indicated  horse  power. 

CONDENSING  ENGINES. 

It  has  been  explained  that  the  atmosphere  exerts  a  pressure 
of  about  15  Ibs.  per  square  inch  on  all  surfaces  with  which  it 


*  This  quantity  is  to  be  taken  as  the  M.  E.  P.  when  finding  steam  con- 
sumption of  compound  engine. 


HANDBOOK    ON    ENGINEERING.  233 

is  in  contact.  The  atmosphere  is  in  contact  with  one  side  of 
mi  engine  piston  when  the  exhaust  is  open",  and,  consequently, 
the  steam  in  pushing  the  piston  forward,  has  to  overcome  this 
atmospheric  pressure  of  15  Ibs.  per  square  inch.  The  useful 
pressure  of  steam  is,  therefore,  whatever  pressure  there  is 
above  the  pressure  of  the  atmosphere,  and  this  is  the  pressure 
that  the  steam  gauge  shows.  When  the  gauge  says  60  Ibs.  we 
really  have  75  Ibs.,  but  15  Ibs.  of  it  does  not  count,  because  it 
is  balanced  by  the  atmospheric  pressure  on  the  other  side  of 
the  piston.  If  we  had  sixty-pound  steam  pressing  on  the  pis- 
ton and  could  get  rid  of  the  atmospheric  pressure  on  the  side 
of  the  piston,  the  steam  would  exert  a  force  of  75  Ibs.  per  square 
inch,  a  very  respectable  gain,  indeed.  We  might  remove  the  air 
pressure  by  pumping  it  out,  but  the  amount  of  power  required  in 
doing  the  pumping  would  be  equal  precisely  to  all  gain  hoped  for, 
plus  the  friction  of  the  pump ;  therefore,  there  would  be  an 
actual  loss  in  the  operation.  But  there  is  another  way  of  remov- 
ing the  air  pressure.  It  has  been  explained  that  a  cubic  inch  of 
water  vaporizes  and  expands  into  a  cubic  foot  of  steam  at  atmos- 
pheric pressure.  If,  after  getting  this  cubic  foot  of  steam,  we 
take  the  heat  out  of  it,  we  again  turn  it  into  the  cubic  inch  of 
water.  Assume  the  engine  cylinder  to  hold  just  a  cubic  foot  of 
steam,  and  assume  that  the  stroke  is  complete  and  ready  for  the 
exhaust  valve  to  open  and  permit  this  foot  of  steam  to  escape, 
and  assume  that  this  cubic  foot  of  steam  has  expanded 
down  to  atmospheric  pressure,  that  is,  15  Ibs.,  absolute  pressure. 
Now,  instead  of  opening  the  cylinder  to  the  atmosphere,  we  dose 
the  cylinder  with  cold  water.  The  heat  leaves  the  steam  and 
goes  into  the  water  and  the  steam  turns  to  water,  leaving  in  the 
cylinder  the  condensed  steam  in  the  form  of  a  cubic  inch  of 
water.  The  steam  formerly  filled  the  cylinder,  and  now  it  fills 
but  a  cubic  inch  of  it,  consequently,  we  have  produced  in  the 
cylinder  u  vacuum  which  has  the  effect  of  adding  about  15  Ibs. 


234  HANDBOOK    ON    ENGINEERING. 

per  square  inch,  to  the  force  of  the  steam  on  the  other  side  of  the 
piston,  by  virtue  of  removing  that  much  resistance  to  its  forward 
motion.  The  heat  which  was  in  the  steam  has  gone  into  the  con- 
densing water,  except  the  trifle  that  remains  in  the  cubic  inch  of 
condensed  water.  We  must  get  this  condensed  water  out  of  the 
cylinder,  and  it  will  be  an  advantage  to  pump  it  back  into  the 
boiler,  for  it  is  pure  and  it  is  hot. 

This  is  the  general  principle  of  the  condensing  engine.  It 
gives  us  the  grand  advantage  of  a  heavy  increase  in  the  useful 
pressure  acting  to  push  the  piston  forward  ;  it  gives  us  pure 
water  for  use  in  the  boiler,  and  it  saves  in  the  feed-water  the 
heat  that  would  otherwise  go  out  of  the  exhaust  pipe.  But  it  is 
not  practicable  to  condense  the  steam  in  the  cylinder  by  dosing 
the  cylinder  with  cold  water.  In  practice,  the  steam  is  allowed 
to  go  into  a  separate  condensing  vessel,  called  the  condenser. 
The  condenser  is  precisely  the  opposite  of  the  boiler.  The  boiler 
is  the  machine  for  putting  heat  into  the  steam  to  vaporize  it,  and 
the  condenser  is  the  machine  for  taking  heat  out  of  the  steam  and 
turning  it  into  water  again.  In  the  condensing  engine,  one  of 
these  machines  is  pushing  on  the  piston  and  the  other  machine  is 
pulling  on  the  piston.  The  gain  by  condensing  is  so  great  that 
it  is  a  profitable  piece  of  business  to  apply  a  condenser  to  any 
large  non-condensing  engine.  The  condenser  requires  a  pump  to 
withdraw  the  water  of  condensation,  and  this  pump  must  be  in 
reality  an  air-pump.  In  practice,  they  employ  an  air-pump  and 
condenser  combined  in  one  structure,  separate  from  the  engine, 
and  driven  either  by  rod  connection  from  the  engine,  or  by  a  belt 
from  the  engine,  or  by  an  independent  steam  pump.  The  arrange- 
ment will  depend  much  upon  the  situation.  The  belt-driven  pump 
permits  of  the  condenser  being  set  in  any  convenient  position 
independent  of  the  engine. 


HANDBOOK    ON    ENGINEERING.  235 


CONDENSERS. 

When  steam  expands  in  the  cylinder  of  a  steam  engine,  its 
pressure  gradually  reduces  and  ultimately  becomes  so  small  that 
it  cannot  profitably  be  used  for  driving  the  piston.  At  this  stage, 
a  time  has  arrived  when  the  attenuated  vapor  should  be  disposed 
of  by  some  method,  so  as  not  to  exert  any  back  pressure  or 
resistance  to  the  return  of  the  piston.  If  there  were  no  atmos- 
pheric pressure,  exhausting  into  the  open  air  would  effect  the 
desired  object.  But,  as  there  is  in  reality  a  pressure  of  about 
14.7  pounds  per  square  inch,  due  to  the  weight  of -the  super- 
incumbent atmosphere,  it  follows  that  steam  in  a  non-condensing 
engine  cannot  economically  be  expanded  below  this  pressure,  and 
must  eventually  be  exhausted  against  the  atmosphere,  which 
exerts  a  back  pressure  to  that  extent. 

It  is  evident  that  if  this  back  pressure  be  removed,  the  engine 
will  not  only  be  aided  by  the  exhausting  side  of  the  piston  being 
relieved  of  a  resistance  of  14.7  pounds  per  square  inch,  but 
moreover,  as  the  exhaust  or  release  of  the  steam  from  the  engine 
cylinder  will  be  against  no  pressure,  the  steam  can  be  expanded 
in  the  cylinder  quite,  or  nearly,  to  absolute  0  of  pressure,  and 
thus  its  full  expansive  power  can  be  obtained. 

Contact,  in  a  closed  vessel,  with  a  spray  of  cold  water,  or  with 
'one  side  of  a  series  of  tubes,  on  the  other  side  of  which  cold 
water  is  circulating,  deprives  the  steam  of  nearly  all  its  latent 
heat,  and  condenses  it.  In  either  case  the  act  of  condensation  is 


236  IIAXDKOOK    OX    ENGINEERING. 

almost  instantaneous.  A  change  of  state  occurs  mid  the  vapor 
steam  is  reduced  to  water.  As  this  water  of  condensation  only 
occupies  about  one  sixteen-himdredths  of  the  space  filled  by 
the  steam  from  which  it  is  formed,  it  follows  that  the  remainder 
of  the  space  is  void  or  vacant,  and  no  pressure  exists.  Now,  the 
expanded  steam  from  the  engine  is  conducted  into  this  empty  or 
vacuous  space,  and,  as  it  meets  with  no  resistance,  the  very  limit 
of  its  usefulness  is  reached. 

The  vessel  in  which  this  condensation  of  steam  takes  place  is 
the  condensing  chamber.  The  cold  water  that  produces  the  con- 
densation is  the  injection  water  ;  .and  the  heated  water,  on  leaving 
the  condenser,  is  the  discharge  water.  To  make  the  action  of  the 
condensing  apparatus  continuous,  the  flow  of  the  injection  water 
and  the  removal  of  the  discharge  water,  including  the  water  from 
the  liquefaction  of  the  steam,  must  likewise  be  continuous. 

The  vacuum  in  the  condenser  is  not  quite  perfect,  because  the 
cold  injection  water  is  heated  by  the  steam  and  emits  a  vapor  of 
a  tension  due  to  the  temperature.  When  the  temperature  is  110 
degrees  Fahr. ,  the  tension  or  pressure  of  the  vapor  will  be 
represented  by  about  4"  of  mercury ;  that  is,  when  the  mercury  in 
the  ordinary  barometer  stands  at  30",  a  barometer  with  the  space 
above  the  mercury  communicating  with  the  condenser,  will  stand 
at  about  26".  The  imperfection  of  vacuum  is  not  wholly  traceable 
to  the  vapor  in  the  condenser,  but  also  to  the  presence  of  air,  a 
small  quantity  .of  which  enters  with  the  injection  water  and  with 
the  steam  ;  the  larger  part,  however,  comes  through  air  leaks  and 
faultly  connections  and  badly  packed  stuffing  boxes.  The  air 
would  gradually  accumulate  until  it  destroyed  the  vacuum,  if 
provision  were  not  made  to  constantly  withdraw  it,  together  with 
the  heated  water  by  means  of  a  pump. 

The  amount  of  water  required  to  thoroughly  condense  the 
steam  from  an  engine  is  dependent  upon  two  conditions :  the  total 
heat  and  volume  of  the  steam,  and  the  temperature  of  the  injection 


HANDBOOK    ON    ENGINEERING.  237 

water.  The  former  represents  the  work  to  be  done,  and  the  latter 
the  value  of  the  water  by  whose  cooling  agency  the  work  of  con- 
densation of  the  steam  is  to  be  accomplished.  Generally  stated, 
with  26"  vacuum,  the  injection  water  at  ordinary  temperature,  not 
exceeding  70°  Fahr.,  from*  20  to  30  times  the  quantity  of  water 
evaporated  in  the  boilers  will  be  required  for  the  complete 
liquefaction  of  the  exhaust  steam.  The  efficiency  of  the  injection 
water  decreases  very  rapidly  as  its  temperature  increases,  and  at 
80°  and  90°  Fahr.,  very  much  larger  quantities  are  to  be  employed. 
Under  the  conditions  of  common  temperature  of  water  and  a 
vacuum  of  26"  of  mercury,  the  injection  water  necessary  per 
H.  P.  developed  by  the  engine,  will  be  from  1J  gallons  per  minute 
when  the  steam  admission  is  for  one-fourth  of  the  stroke,  up  to 
two  gallons  per  minute,  when  the  steam  is  carried  three-fourths  of 
the  stroke  of  the  engine. 


238 


HANDBOOK    ON    ENGINEERING. 


SETTING  THE  PISTON  TYPE  OF  VALVE. 

The  simple  piston  valve  admitting  steam  between  the  pistons 
is,  in  operation,  the  reverse  of  the  plain  D  slide  valve,  which  ad- 
mits steam  at  the  outer  edges,  or  ends  of  the  valve.  To  make 
this  still  clearer  it  may  be  said  that  were  the  live  steam  to  enter 
through  the  exhaust  cavity  of  the  D  slide  valve  its  operation  and 
the  position  of  the  eccentric  relative  to  the  crank  would  be  iden- 


tical   to  that  piston  valve.     Fig.   1   illustrates  the  similarity  of 
action  and  eccentric  positions  were  these  conditions  to  obtain. 

In  these  types  of  valve,  as  ordinarily  employed,  the  steam  is 
admitted  at  the  ends  of  the  slide  valve,  and  between  the  pistons 
or  at  the  middle  of  the  piston  valve.  The  change  from  the  end 
to  the  middle  of  the  valve  necessitates  a  change  in  the  position 
of  the  eccentric  relative  to  the  crank  in  order  to  have  the  direc- 
tion of  rotation  remain  the  same.  The  positions  of  the  eccentric 
when  driving  the  simple  D  valve,  and  the  piston  valve,  are  indi- 


HANDBOOK    ON    ENGINEERING. 


239 


cated  in  Fig.  2.  It  will  be  noticed  that  the  crank  revolves  in  the 
same  direction  in  both  cases,  and  that  when  the  crank  leaves  the 
dead  center,  moving  in  the  direction  of  the  arrow,  the  same  port, 
viz.,  the  one  at  the  head  end  of  the  cylinder,  will  be  opened  at  the 
same  time  and  to  the  same  extent.  This  proves  the  positions  as 
shown  to  be  correct  and  illustrates  why  the  eccentric  must  be 
moved  in  the  same  direction  the  engine  is  to  run  with  theZ)  valve, 
and  in  the  opposite  direction  with  the  piston  valve,  in  order  to 
secure  the  same  direction  of  rotation  in  the  engine. 


Fiff.2 

f 


When  setting  valves  it  is  a  good  plan  to  obtain  as  much  uni- 
formity of  methods  as  possible,  because  of  the  liability  to  con- 
fusion when  methods  involving  different  movements  of  the 
eccentric  are  employed.  In  all  the  directions  that  follow  it  is 
assumed  that  the  crank  is  placed  on  the  dead  center  (sae  page 
195)  nearest  the  cylinder  so  that  when  setting  the  different  styles 
of  valves,  the  same  steam  port  will  always  be  opened  first,  namely, 
the  one  at  the  head  end  of  the  cylinder.  The  engine,  it  will  be 


240  HANDBOOK    ON    ENGINEERING. 

seen,  is  thus  treated  as  though  it  contained  but  one  steam  port, 
which  greatly  simplifies  matters. 

In  order  to  show  that  each  particular  form  of  valve  of  the  same 
type  does  not  require  different  methods  for  its  proper  adjustment, 
both  the  simple  piston  valve  andjthe  main  valve  of  the  round  riding 
cut-off  are  illustrated  together,  the  same  directions  applying  to 
both. 

Where  marks  appear  upon  the  valve  stem,  or  seat,  it  becomes 
an  easy  matter  to  set  a  valve  quickly  and  correctly  but  when  these 
do  not  appear  a  different  method  must  be  pursued  for  obtaining 
them.  First  remove  the  chest  covers  at  both  ends  of  the  chest 

.e»yM  of  Gape*-  Me 

»•  f          ° 


£c/r  efc 

Fig.  3 

and  also  the  valve  (both  styles)  from  the  chest  and  lay  it  upon  a 
clean  place  on  the  floor,  or  bench.  Procure  a  piece  of  sheet  steel 
about  y1^  inch  thick  and  file  it  to  the  form  shown  in  Fig.  3. 
Make  the  length  of  the  gauge  thus  formed  equal  to  the  thickness 
of  the  piston  on  the  valve  plus  the  lead,  which  may  betaken  as  -^ 
inch.  Replace  the  valve  in  the  chest  and  connect  it  to  the  valve 
stem.  Turn  the  eccentric  from  one  extreme  position  to  the  other 
and  see  that  the  valve  opens  the  ports  an  equal  amount.  It  is  not 
necessary  that  the  ports  be  opened  exactly  wide,  the  object  being 
to  secure  exactly  the  same  opening  at  each  end  of  the  valve.  If 
the  head  end  port  is  opened  farther  than  the  other,  the  eccentric 


HANDBOOK    ON    ENGINEERING.  241 

rod  should  be  lengthened  an  amount  equal  to  one-half  the  differ- 
ence, and  should  the  port  at  the  crank  end  be  opened  farthest, 
tte  eccentric  rod  should  be  shortened  a  like  amount. 

Turn  the  eccentric  to  the  extreme  position  farthest  from  the 
cylinder.  Then  place  the  small  end  of  the  gauge  against  the  inner 
edge  of  the  port,  and  with  a  scriber  make  a  fine  line  (a)  on  the 
seat  as  shown  in  Fig.  4.  Remove  the  gauge,  and  turn  the  eccen- 
tric in  the  same  direction  the  engine  is  to  run  until  the  end  of  the 
valve  reaches  the  fine  line  on  the  seat.  Secure  the  eccentric  to 
the  shaft,  being  careful  not  to  move  the  eccentric  in  either  direc- 
tion. Now  turn  the  crank  in  the  direction  it  is  to  run  UDtil  the 
eccentric  reaches  the  extreme  position  nearest  the  cylinder.  The 
gauge  is  now  placed  against  the  edge  of  the  opposite  port  and  a 


fig.  4 


fine  line  drawn  on  the  seat,  at  the  end  of  the  gauge,  in  the  same 
manner  as  shown  in  Fig.  4.  Turn  the  crank  to  the  dead  center 
farthest  from  the  cylinder  when  the  end  of  the  valve  should  have 
just  reached  the  line  on  the  seat.  If  it  does  not,  the  crank 
should  be  turned  sufficiently  to  enable  the  distance  between  the 
valve  and  the  mark,  being  measured.  The  eccentric  rod  is  then 
to  be  adjusted  so  as  to  move  the  valve  a  distance  equal  to  one- 
half  of  what  the  valve  lacks  of  exactly  reaching  the  line  on  the 
seat.  The  valve  will  then  open  both  ports  to  the  extent  of  the 

10 


242  HANDBOOK    ON    ENGINEERING. 

lead  when  the  crank  occupies  the  exact  dead  centers.  It  is  very 
desirable  to  have  a  method  of  setting  the  valve  without  removing 
the  chest  covers.  By  the  aid  of  simple  gauges  this  can  be  readily 
accomplished.  Take  a  piece  of  steel  wire  and  sharpen  the 
ends  and  bend  into  the  form  shown  in  Fig  5.  With  a  prick 
punch  make  a  mark  (&)  on  the  guide  block,  place  one  end  of 
gauge  in  this  mark  and  make  another  mark  (c)  where  the  opposite 
end  of  the  gauge  touches  the  valve  stem.  This  gauge  enables 
the  valve  stem  being  disconnected  from  the  valve  stem  guide 
block,  and  the  chest  cover  put  on,  and  the  stem  afterward  con- 
nected up  again  in  exactly  the  same  position  (see  page  ). 
Having  made  this  second  gauge,  place  the  crank  on  the  exact 
dead  center  nearest  the  cylinder.  Then  make  a  prick  punch  mark 
(c?)  on  the  stuffing  box,  place  one  end  of  the  gauge  in  this  mark 
and  then  make  a  second  mark  (e)  where  the  other  end  of  the 
gauge  touches  the  valve  stem.  It  will  readily  be  seen  that  when 
testing  the  setting  of-  the  valve  all  that  is  necessary  is  to  place 
the  crank  on  the  dead  center  nearest  the  cylinder,  then  place  the 
gauge  the  mark  (d)  on  the  stuffing-box,  and  have  the  eccentric 
moved  until  the  punch  mark  (e)  on  the  valve  stem  falls  under 
the  point  of  the  gauge.  The  valve  will  then  have  opened 
the  port  to  the  extent  of  the  lead,  because  it  was  in 
this  position  when  the  gauge  and  the  marks  were  first 
made.  If  the  punch  marks  are  nicely  made  and  not  too  large 
the  extent  of  the  lead  opening  may  be  measured  at  both  ports, 
by  turning  the  crank  to  the  opposite  dead  center  and  making  a 
second  punch  mark  (/)  on  the  valve  stem  by  means  of  the  gauge. 
These  two  guages  should  be  carefully  preserved  from  injury  and 
from  being  mislaid  so  that  in  case  of  emergency,  such  as  the 
slipping  of  an  eccentric,  the  latter  can  be  returned  to  its  correct 
position  without  unnecessary  loss  of  time. 


HANDBOOK   ON   ENGINEERING. 


243 


SETTING  THE  CUT=OFF  VALVE. 

The  following  directions  are  applicable  to  both  the  flat  slide 
and  the  round  types  of  cut-off  valves. 

The  point  of  latest  cut-off  is  seldom  known  exactly  by  the 
average  engineer  because  of  its  unimportance  while  the  engine  is 
in  running  order,  and  as  this  point  varies  with  different  engines 
it  is  advisable  to  discard  it  as  an  element  in  valve  setting.  First 
place  the  main  valve  in  its  position  of  mid-travel,  that  is,  place 
it  centrally  over  the  ports.  This  may  be  accomplished  by  finding 
the  center  between  the  punch  marks  (/)  and  (e)  on  the  valve 
stem,  bringing  the  center  mark  g  under  the  point  of  the  gauge  in 
the  manner  shown  in  Fig.  5.  The  travel  of  the  cut-off  valve  must 
first  be  equalized  which  is  accomplished  by  turning  the  cut-off 


eccentric  to  its  extreme  positions  and  noting  the  travel  of  the 
cut-off  valve  over  the  ports  of  the  main  valve.  The  cut-off  eccen- 
tric rod  should  be  lengthened  or  shortened  so  that  the  cut-off 
valve  will  travel  evenly  over  the  ports  in  the  main  valve.  This, 
of  course,  is  obtained  by  measuring  the  distance  from  the  edge 
of  the  ports  in  the  main  valve  to  the  ends  of  the  cut-off  valve  when 
the  latter  occupies  its  extreme  positions. 

First,  assume  the  engine  to  have  a  fixed,  or  a  hand-adjusted 
cut-off,  and  that  the  cut-off  valve  is  to  be  set  to  cut  off  steam  at 


244  HANDBOOK    ON    ENGINEERING. 

one-half  stroke.  Place  the  crank  on  the  dead  center  (see  page 
195)  and  the  full  part  of  the  cut-off  eccentric  the  same.  Then 
measure  off  one-half  the  length  of  the  stroke  from  the  end  of  the 
cross-head  as  in  Fig.  6  and  make  a  light  line  /  on  the  guide.  Turn 
the  engine  in  the  direction  it  is  to  run  until  the  end  of  cross-head 


reaches  the  line  /  on  the  guide.  The  piston  will  now  have  com- 
pleted one-half  its  stroke.  Turn  the  cut-off  eccentric  in  the 
direction  the  engine  is  to  run  until  the  cut-off  valve  opens  the 
port  in  the  main  valve  wide  and  just  closes  the  port  again  in  the 
main  valve. 

Secure  the  cut-off  eccentric  to  the  shaft  at  this  point. 
Turn  the  crank  over  to  the  opposite  d^ad  center  and  far  enough 
beyond  the  center  so  that  the  same  end  of  the  crosshead  will  have 
again  reached  the  line  (/)  on  the  guide  as  in  Fig.  6.  The  piston 
will  now  have  completed  one-half  of  the  return  stroke  and  the 
cut-off  valve  should  have  just  closed  the  port  in  the  main  valve. 
If  the  cut-off  valve  has  moved  too  far,  or  not  far  enough,  measure 
the  amount  it  lacks  of  just  closing  the  port  and  then  adjust  the 
cut-off  eccentric  rod  an  amount  equal  to  one-half  the  amount  of 


HANDBOOK   ON    ENGINEEKING.  245 

the  discrepancy.  The  cut-off  valve  will  then  close  the  port  in  the 
main  valve  at  exactly  the  same  point  in  both  forward  and  return 
strokes. 

When  an  automatic  cut-off  engine,  in  which  the  cut-off 
eccentric  is  operated  by  a  shaft  governor,  first  block  out  the 
weights  to  their  extreme  position  or  against  the  stops,  the  travel 
of  the  cut-off  valve  having  been  previously  equalized  in  the 
manner  explained  above.  Then  turn  the  crank  to  the  dead  center, 
preferably  the  one  nearest  the  cylinder,  and  turn  the  full  port  of 
the  cut-off  eccentric  to  the  same  position  as  a  starting  point. 
Then  turn  the  eccentric  in  the  direction  the  engine  is  to  run  until 
the  cut-off  valve  opens  the  port  in  the  main  valve  to  the  extent  of 
the  lead  or  from  -fa  to  -f^  inch.  Secure  the  governor  wheel  to 
the  shaft  at  this  point.  Turn  the  crank  to  the  opposite  dead 
center  and  see  that  the  cut-off  valve  has  opened  the  port  in  the 
main  valve  to  the  same  extent.  If  it  has  not  done  so,  adjust  the 
length  of  the  eccentric  rod  an  amount  equal  to  one-half  the  differ- 
ence between  the  two.  lead  openings.  Take  out  the  blocks  and 
the  work  will  be  completed.  It  will  readily  be  understood  that, 
were  the  speed  of  the  engine  to  reach  a  point,  where  the 
governor  weights  strike  the  stops,  the  cut-off  valve  will  admit 
only  steam  enough  to  fill  the  clearance,  which  should  always  be 
done,  because  while  it  does  not  tend  to  accelerate  the  speed  it 
does  prevent  forming  a  vacuum  in  the  cylinder,  and  from  drawing 
in  whatever  may  happen  to  be  in  the  vicinity  of  the  end  of  the 
exhaust  pipe.  The  point  of  latest  cut-off  will  then  take  care  of 
itself  and  will  occur  at  that  point  for  which  the  valve  and  gear 
were  designed. 

FLAT  VALVE  RIDING  CUT-OFF. 

In  medium  and  slow  speed  engines  it  is  very  desirable  to  have 
a  uniform  point  of  release  and  constant  compression.  If  the 
engine  is  of  the  automatic  cut-off  variety  the  point  of  cut-off  will 


246  HANDBOOK    ON    ENGINEERING. 

necessarily  change  with  each  change  of  load,  and  if  the  steam  is 
released,  and  the  point  of  compression  determined  by  the  valve 
effecting  the  out-off ,  it  is  plain  that  as  the  cut-off  varies,  the  point 
of  exhaust  and  of  compression  must  also  vary  proportionately. 
In  order  to  secure  a  uniform  amount  of  lead,  a  constant  point  of 
release  and  of  compression,  it  is  necessary  that  the  valve  deter- 
mining these  points  be  given  a  constant  travel.  Then  in  order  to 
produce  a  variable  cut-off  a  separate  cut-off  valve  must  be  pro- 
vided. This  is  the  object  of  the  riding  cut-off.  The  main  valve 
determines  the  lead,  point  of  release  and  point  of  exhaust  closure 
and  as  the  travel  of  the  main  valve  relative  to  the  crank  is  un- 
changeable these  functions  always  remain  the  same.  The  duty  of 
the  cut-off  valve  is  simply  to  close  the  ports  in  the  main  valve, 
and  it  determines  the  point  of  cut-off  only.  It  will  be  seen,  there- 
fore, that  with  this  arrangement  of  valves,  constant  lead,  exhaust 


Ftg.r 


opening  and  constant  compression  are  secured  while  the  point  of 
cut-off  is  constantly  changing  with  the  load.  Keeping  these  fun- 
damental facts  in  mind,  it  is  readily  seen  that  the  main  valve  of 
the  riding  cut-off  is,  in  operation,  exactly  the  same  as  the  ordi- 
nary D  slide  valve  having  a  fixed  travel.  In  the  riding  cut-off 
the  travel  of  the  cut-off  valve  is  fixed,  so  far  as  length  of  stroke 
is  concerned,  but  the  times  of  closing  the  ports  in  the  main  valve 
are  variable  and  are  determined  either  by  hand  adjustment  or  by 
the  governor,  depending  upon  whether  the  engine  is  a  throttling 
or  an  automatic  cut-off  engine.  The  points  of  cut-off  are 
changed  by  rolling  the  cut-off  eccentric  around  on  the  shaft. 


HANDBOOK    ON    ENGINEERING.  247 

The  farther  the  cut-off  eccentric  is  set  in  advance  of 
the  crank  the  earlier  in  the  stroke  will  steam  be  cut  off, 
and,  the  nearer  together  the  two  eccentrics  are  set,  the  later 
will  the  cut-off  occur.  The  main  valve  is  generally  designed 
to  cut  off  steam  at  |-  or  J  stroke,  so  that  if  the  cut- 
off valve  and  main  valve  move  together  the  point  of  cut-off 
will  be  determined  by  the  main  valve  and  will  occur  at  %  or 
J  stroke.  Now  if  the  cut-off  eccentric  (c)  be  set  ahead  of 
the  main  eccentric  (m)  as  in  Fig.  7,  it  will  reach  the  end  of  its 
stroke  and  start  back  again  before  the  main  eccentric  has  com- 
pleted the  stroke,  thus  the  cut-off  valve  moves  in  one  direction 
and  the  main  valve  in  the  opposite  direction  and  that  point  in  the 
piston  stroke  at  which  the  centers  of  the  two  valves  meet  will  be 
the  point  of  cut-off.  If  the  cut-off  eccentric  be  set  nearly  oppo- 
site the  main  eccentric  it  is  evident  that  when  the  main  valve 
reaches  one-half  of  the  outward  stroke  the  cut-off  valve  will  have 
reached  nearly  one-half  of  the  return  stroke  and  the  cut-off  will 
occur  at  about  this  point  in  the  piston  stroke,  which  will  be 
approximately  one-fourth  stroke. 


Figs 


When  setting  the  valves,  first  equalize  the  port  opening  of  the 
main  valve.  This  is  accomplished  by  turning  the  main  eccentric 
from  one  extreme  position  to  the  other  seeing  that  both  ports  in 
the  valve  seat  leading  into  the  cylinder  are  opened  exactly  the 
same  amount.  It  is  not  necessary  that  these  ports  be  opened 
exactly  wide ;  the  object  is  to  see  that  both  ports  are  opened  to 
the  same  extent  when  the  eccentric  is  in  its  extreme  positions. 


248  HANDBOOK   ON   ENGINEERING. 

Having  equalized  the  travel  of  the  main  valve  place  the  crank  on 
the  dead-center,  see  page  195,  and  turn  the  full  side  of  the  main 
eccentric  to  a  corresponding  position.  Then  turn  the  eccentric 
in  the  direction  the  engine  is  to  run  until  the  port  in  the  main 
valve,  corresponding  to  the  position  of  the  crank  or  piston,  opens 
the  port  leading  into  the  cylinder  to  the  amount  of  the  lead,  which 
may  be  taken  as  -J^-  inch.  Now,  before  moving  the  engine  make 
a  gauge  of  the  form  shown  in  Fig.  8.  Put  a  punch  mark  on  the 
stuffing-box,  and,  placing  one  end  of  the  gauge  in  this  mark,  draw  a 
fine  line  on  the  valve  stem  at  the  opposite  point  of  the  gauge. 
Turn  the  crank  to  the  opposite  dead-center  and  note  the  amount 
of  lead  opening.  If  it  is  not  the  same  as  first  obtained  adjust  the 
eccentric ^rod  to  the  extent  of  one-half  the  difference.  Then  place 
the  gauge  in  the  punch  mark  on  the  stuffing-box  and  draw  a  fine 
line  at  the  opposite  point  of  the  gauge. 

Turn  the  crank  back  again  to  its  first  position  and  note  the 
lead.  If  it  is  found  to  be  equal  at  both  ends,  apply  the 
gauge  again  and  this  time  make  a  light  punch  mark  at  the  outer 
point  of  the  gauge.  Then  put  a  similar  punch  mark  on  the  fine 
line  representing  the  lead  at  the  opposite  end  of  the  valve  travel. 
By  means  of  these  marks  it  will  be  possible  to  set  the  main  valve 
correctly  without  removing  the  steam  chest  cover.  Now  divide 
the  distance  between  the  two  punch  marks  and  put  a  third  punch 
mark  at  the  middle.  Turn  the  crank  around  in  the  direction 
the  engine  is  to  run  until  the  middle  punch  mark  falls  under  the 
outer  point  of  the  gauge.  The  main  valve  will  now  be  at  the 
middle  of  its  travel.  The  travel  of  the  cut-off  valve  must  now  be 
equalized  so  that  the  latter  valve  will  travel  equal  distances  be- 
yond the  ports  in  the  main  valve.  This  is  accomplished  in  pre- 
cisely the  same  manner  as  with  the  main  valve.  Having 
equalized  the  travel  of  the  cut-off  valve,  turn  the  crank  in  the 
direction  the  engine  is  to  run  until  the  cross-head  reaches  the  point 
in  the  stroke  at  which  the  cut-off  is  to  occur,  which  is  to  be  de- 


HANDBOOK    ON    ENGINEERING.  249 

signaled  by  a  line  drawn  on  the  guide.  Now  turn  the  cut-off 
eccentric  in  the  same  direction  until  it  reaches  its  extreme  position. 
Continue  to  move  the  eccentric  until  the  cut-off  valve  just  closes 
the  port  in  the  main  valve.  Secure  the  cut-off  eccentric  to  the 
shaft  at  this  point.  Then  turn  the  crank  around  until  the  cut- 
off takes  place  on  the  return  stroke  and  see  if  it  corresponds  to 
the  point  on  the  previous  stroke.  If  not,  adjust  the  length  of 
the  cut-off  eccentric  rod  an  amount  equal  to  one-half  the  differ- 
ence. 

It  is  important  to  be  able  to  set  the  cut-off  valve  also  without 
taking  off  the  steam  chest  cover.  One  punch  mark  only  is  re- 
quired for  this.  Place  the  main  valve  in  its  position  of  mid- 
travel  by  means  of  the  gauge.  Then  put  a  punch  mark  on  the 
stuffing-box  of  the  cut-off  valve  stem  and,  placing  the  gauge  in 
this  mark,  put  another  at  the  opposite  end  of  the  gauge  on  the 
cut-off  valve  stem.  See  Fig.  8. 

This  method  furnishes  a  simple  and  quick  means  of  setting 
both  the -main  and  cut-off  valves  when  an  eccentric  slips.  All 
that  is  necessary  is  to  place  the  crank  on  the  dead-center  and 
bring  the  proper  punch  mark  under  the  point  of  the  gauge.  Then 
bring  the  main  valve  to  its  position  of  mid-travel  and  with  the 
gauge  bring  the  cut-off  valve  to  its  proper  position. 

The  foregoing  directions  for  setting  the  cut-off  eccentric  apply 
to  the  hand-adjusted  gear  only.  When  the  cut-off  eccentric  is 
operated  by  the  governor,  the  travel  is  equalized  in  precisely 
the  same  manner  as  when  hand-adjusted.  After  equalizing  the 
travel  of  the  cut-off  valve,  place  the  crank  on  the  dead-center. 
The  main  valve,  which  is  invariably  set  first,  will  now  open  the 
port,  corresponding  to  the  .position  of  the  piston  to  the  extent  of 
the  lead.  Next  block  out  the  governor  weights  against  the  stops. 
Turn  the  full  side  of  the  cut-off  eccentric  to  correspond  to  that  of 
the  crank  as  a  starting-point.  Then  turn  the  cut-off  eccentric 
(governor  wheel),  around  on  the  shaft  in  the  direction  the  engine 


250  HANDBOOK    ON    ENGINEERING. 

is  to  run  until  the  port  in  the  main  valve  is  opened  to  the  extent 
of  the  lead.  Secure  the  governor  wheel  to  the  shaft.  Turn  the 
crank  to  the  opposite  dead-center  and  see  that  the  cut-off  valve 
opens  the  port  in  the  main  valve  to  the  same  extent.  If  the 
difference  is  slight  it  may  be  equalized  by  adjusting  the  length 
of  the  cut-off  eccentric  rod  an  amount  equal  to  one-half  the  differ- 
ence of  the  lead  openings.  Should  the  difference  be  great,  say, 
one-half  inch,  that  is,  should  the  cut-off  valve  lack  one-half  inch 
of  opening  the  port  in  the  main  valve,  it  indicates  that  the  cut-off 
valve  is  too  long,  which  is  apt  to  be  the  case  where  two  cut-off 
valves  are  employed  on  the  same  stem.  The  valve  may  be 
shortened  by  moving  the  two  parts  closer  together,  moving  each 
part  one-fourth  of  the  amount  the  cut-off  valve  lacked  of  opening 
the  port  in  the  main  valve.  Then  begin  over  again  to  set  the 
cut-off  eccentric  and  if  the  adjustments  have  been  carefully  made 
it  will  open  the  ports  correctly  at  both  ends  of  the  main  valve. 
After  fastening  the  main  eccentric  and  the  governor  wheel  securely 
to  the  shaft  remove  the  blocks  from  the  governor  weights  and  the 
job  will  be  finished. 

When  the  valve  gear  contains  a  rocker-shaft  of  the  construc- 
tion shown  on  page  322,  the  eccentric  must  be  turned  in  the 
opposite  direction  to  that  in  which  the  engine  is  to  run,  until  the 
main  valve  opens  the  port  leading  into  the  cylinder,  to  the  extent 
of  the  lead. 


HANDBOOK    ON    ENGINEERING.  251 


CHAPTER     XII. 
THE  STEAM  ENGINE.  —  CONTINUED. 

Work  consists  of  the  sustained  exertion  of  force  through  space. 
The  unit  of  work,  the  foot-pound,  is  a  force  of  one  pound  exerted 
through  one  foot  space.  The  work  done  in  lifting  one  pound  ten 
feet,  or  ten  pounds  one  foot,  is  ten-foot  pounds. 

Power  is  the  rate  of  work,  or  the  number  of  foot-pounds  ex- 
erted in  a  unit  of  time.  The  unit  of  power  is  the  horse-power, 
and  equals  33,000  foot-pounds  exerted  in  a  minute,  or  550  foot- 
pounds exerted  in  a  second,  or  1,980,000  foot-pounds  exerted  in 
an  hour.  An  engine  developing  fifty-horse  power,  exerts  27,500 
foot-pounds  per  second,  1,650,000  foot-pounds  in  a  minute.  It 
could  raise  (friction  neglected)  41,250  pounds  forty  feet  in  one 
minute. 

A  belt  running  over  a  pulley  at  4,000  feet  per  minute,  pulling 
with  a  force  of  240  pounds  (fair  load  for  a  4-inch  belt)  will 
transmit 

240x4.000 

—  oo  Ann  —  equal  thirty  horse-  power  (nearly). 
oo  ,uUO 

If  moving  at  1,100  feet  per  minute,  the  result  would  be 

240x1,100 

equal  eight  horse-power. 


A  gear-wheel,  the  cogs  of  which  transmit  a  pressure  of  1,800 
pounds  (fair  load  for  1J"  pitch  6"  face)  to  the  cogs  of  its  mate, 
the  periphery  velocity  of  the  wheels  being  ten  feet  per  second, 
transmits 

1,800  x  10 

equal  thirty-three  horse  power  nearly. 


252  HANDBOOK    ON    ENGINEERING. 

If  speed  was  360  feet  per  minute,  it  would  transmit 

1,800x360 

— ot>  ~~~ —  equal  twenty  horse-power  nearly. 

The  horse-power  developed  by  a  steam  engine  consists  of  two 
primary  factors,  Piston  Speed  and  Total  Awr<nj<>  /V^.s.s/</v  of 
steam  upon  the  piston. 

Piston  speed  depends  upon  the  stroke  of  engine  and  the  num- 
ber of  revolutions  per  minute.  An  engine  with  stroke  of  twelve 
inches,  making  oOO  revolutions  per  minute,  has  a,  piston  speed  of 

2  x  12  x  300 

— rg —   -  equal  600  feet  per  minute. 

Piston  speed  of  an  engine  with  24"  stroke  at  150  revolutions 
per  minute : 

2x24x150 

— ^ —  -  equal  600  feet  per  minute. 

Total  average  pressure  depends  on  area  of  piston  and  mean 
effective  pressure  per  square  inch  exerted  on  piston  throughout 
stroke.  The  mean  effective  pressure  (M.  E.  P.)  in  any  case  can 
only  be  accurately  obtained  by  means  of  the  steam  engine  indi- 
cator, and  depends  upon  the  load  engine  is  carrying. 


GENERAL  PROPORTIONS. 

Diameter  of  steam  pipes : 

Slide-valve  engine,    J    diameter    of    piston. 
Automatic  high-speed  engines,  J  diameter  of  piston. 
Corliss  engine,  T3^  diameter  of  piston. 

Diameter  of  exhaust  pipes : 

Slide-valve  engine,  .-J-  diameter  of  piston. 
Automatic  high-speed  engine.  |  diameter  of  piston. 
Corliss  ensrine.  -!•  to  3-  diameter  of  piston. 


Automatic  high-speed  engine.  |  cliametc 
Corliss  engine,  -|  to  |  diameter  of  pistoi 


HANDBOOK    ON    ENGINEERING.  253 

Displacement  of  piston 

Clearance  spaces :  in  one  stroke. 

Slide-valve  engine 0.06  to  0.08 

Automatic  high-speed  engine,  single  valve        .  0.08  to  0.15 

Automatic  high-speed  engine,  double  valve      .  0.03  to  0.05 
Automatic  cut-off  engine,   Corliss   type,  long 

stroke 0.02  to  0.04 

Weights  of  engines  per  rated  horse-power  : 

Slide-valve  engine 125  to  135  Ibs. 

Automatic  high-speed  engine        90  to  120  Ibs. 

Corliss  engine      . 220  to  250  Ibs. 

Fly-wheels,  weight  per  rated  horse-power : 

Slide-valve  engine 33  Ibs. 

Automatic  high-speed  engine 25  to  33  Ibs. 

(According  to  size  and  speed.) 
Corliss  engine 80  to  120  Ibs. 

(According  to  size  and  speed.) 

RULES  FOR  FLY=WHEEL  WEIGHTS,  SINGLE  CYLINDER 
ENGINES. 

Let  d  =  diameter  of  cylinder  in  inches. 
S  =  stroke  of  cylinder  in  inches. 
D  =  diameter  of  fly-wheel  in  feet. 
R  =  revolutions  per  minute. 
W  =  weight  of  fly-wheel  in  pounds. 

d2  S 
For  slide-valve  engines,  ordinary  duty    .      W-  =  350,000  jjrjgi 

d?  S 
For  slide-valve  engines,  electric  lighting.      \V -~  700,000  ~™~JM 

d2  ti 
For  automatic  high-speed  engines     .      .      }\r  --•=  1,000,000  rjrjxt 


254  HANDBOOK    ON    ENGINEERING. 

d2  S 
For  Corliss  engines,  ordinary  duty    .      .      W=  700,000    ^r™ 


For  Corliss  engines,  electric  lighting       .      W=  1,000,000  v^—™ 


The  Russell  Engine. 

SETTING  THE  VALVE  ON  A  RUSSELL  ENGINE,  SINGLE  VALVE 
TYPE.  THE  SAHE  PRINCIPLE  LAID  DOWN  IN  THE  SET= 
TING  OF  THE  COHMON  SLIDE  VALVE  MUST  BE  ADHERED 
TO. 

The  style  of  valve  is  shown  in  cut,  Fig.  1.  It  is,  to  some 
extent,  a  moving  steam  chest  with  the  steam  all  within  itself, 
admitting  only  enough  steam  into  the  chest  to  keep  the  valve  to 
its  seat,  against^  the  maximum  -tendency  to  leave  it.  This  pres- 
sure in  the  chest  is  found  with  the  valve  as  at  present  propor- 
tioned, to  be  about  45  per  cent  of  that  contained  within  the 
valve.  The  cut  shows  the  valve  and  section  of  cylinder  so 
plainly  as  to  render  any  detailed  explanation  of  same  almost 
unnecessary. 


HANDBOOK    ON    ENGINEERING. 


255 


The  eccentric  operating  the  valve  is  under  control  of  the  gover- 
nor, as  shown  in  cut  Fig.  2,  which  regulates  the  speed  of  the 
engine  by  sliding  the  eccentric  across  the  shaft,  either  forward  or 
backward,  as  the  weights  change  their  position,  thereby  cutting 
the  steam  off  earlier  or  later  in  the  stroke,  as  the  governor,  or 
more  properly,  the  weights  adjust  themselves  to  the  load. 

When  the  eccentric  is  moved  across  the  shaft  in  a  direction 
that  reduces  its  eccentricity,  the  steam  is  cut  off  earlier  in  the 


(FJCK  1) 

stroke  ;  when  the  eccentric  is  moved  in  the  opposite  direction, 
the  steam  is  cut  off  later  in  the  stroke.  The  extreme  range  of 
this  cut-off  is  from  0  to  J  of.  the  engine's  stroke,  and  this 
whole  range  of  adjustment  is  under  complete  control  of  the 
governor. 

To  preserve  a  certain  determined  speed  with  the  smallest  pos- 
sible variation,  as  changes  occur  in  the  load  or  pressure,  is  the 
function  of  the  governor.  The  cut-off  must  always  be  propor- 
tioned to  the  load.  When  the  engine  is  running  empty,  the  steam 
is  cut  off  at  the  beginning  of  the  stroke  and  the  governor  weights 
are  at  their  extreme  outer  position.  With  a  heavy  load,  steam 
follows  further  and  the  weights  are  nearer  their  inner  position.  Be- 

16 


25G 


HANDBOOK    ON    ENGINEERING. 


tween  these  two  limits,  any  number  of  positions  of  the  weights,  and 
corresponding  angular  positions  of  the  eccentric,  may  be  had  ;  and 


Fig.  2. 

as  the  steam  is  thus  adapted  to  the  load  in  each  position,  it  follows 
that  a  slight  increase  or  decrease  in  speed  must  make  a  change  in 
the  cut-off  and  bring  the  engine  again  to  standard  speed. 


HANDBOOK    ON    ENGINEERING.  257 

In  setting1  the  valves  it  is  necessary  to  mark  the  ports  in  the 
valve  face  at  the  outer  edge  of  the  steam  chest,  and  also  to  mark 
on  the  back  of  the  valve  the  ports  in  its  face,  so  that  it  may  be 
adjusted  after  being  placed  in  the  chest,  in  which  position  it  pre- 
sents a  blank  surface  that,  without  these  marks,  would  afford  no 
means  for  knowing  its  position. 

In  placing  the  valve  in  the  chest,  see  that  it  fits  perfectly 
against  the  seat  and  that  the  bottom  bearing,  on  which  the  valve 
rides,  is  at  right  angles  to  the  valve  seat,  and  in  such  a  condition 
that  the  valve  will  not  be  tipped  away  from  its  seat,  but  rather 
against  it.  This  latter  condition  will  be  insured  by  easing  off 
the  bottom  strip  at  the  inner  corner,  so  that  the  valve  would 
bear  hardest  at  the  outer  edge.  The  hinge  nut,  into  which  the 
valve  stem  is  screwed,  as  well  as  its  trunnion  bearings,  should 
fit  so  that  the  valve  lays  closely  to  its  seat,  rather  than  be  held 
away  from  it. 

Having  extended  the  marks  of  the  ports  as  well  in  the  valve 
seats  as  in  the  valve  itself,  to  the  outside,  it  now  becomes  neces- 
sary to  get  the  center  of  the  travel  of  the  eccentric  and  connect 
the  valve  and  rod,  so  that  the  valve  will  travel  equally  on  either 
side  of  this  center.  The  throw  of  the  eccentric  leads  the  crank  in 
the  direction  the  engine  runs,  and  with  the  eccentric  properly 
located,  as  it  cannot  help  being,  because  it  is  attached  to  the 
governor  and  the  governor  is  keyed  to  the  shaft,  the  lead  will 
remain  the  same  with  the  governor  weights  in  their  outer  as  well 
as  in  their  inner  positions. 

These  valves  are  usually  marked  with  the  engine  on  the  center 
at  either  end,  marks  corresponding  with  the  admission  edges  of 
valve  and  seat.  The  hinge  nut  connection  makes  it  convenient  to 
examine  these  valves  without  disconnecting  or  disturbing  any 
adjustments  made.  The  valve  rod  has  right  and  left-hand  threads 
for  adjustment,  and  final  adjustment  can  be  made  without  taking 
off  the  steam  chest  cover. 

17 


258 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING.  259 

THE    PORTER=ALLEN    STEAM    ENGINE,    MADE    BY    THE 
SOUTHWARK  FOUNDRY  &  flACHINE  CO. 

This  engine  claims  the  distinction  of  being  the  original  and 
most  perfect  type  of  the  high-speed  steam  engine.  In  truth, 
however,  it  should  not  be  termed  a  high-speed  engine.  Relatively, 
indeed,  to  those  speeds  to  which  it  has  hitherto  been  found  neces- 
sary to  limit  the  motion  of  engines,  its  speed  is  high ;  but  consid- 
ered absolutely,  and  as  it  appears  to  all  persons  accustomed  to  it, 
this  engine  is  ordinarily  run  at  what  is  undoubtedly  the  natural, 
and  on  all  accounts,  the  desirable  speed  at  which  a  properly 
designed  and  constructed  steam  engine  ought  to  be  run,  for  ordi- 
nary purposes  ;  while  this  is  much  below  the  speed  of  which  it  is 
capable,  and  at  which  it  is  run  with  entire  success,  in  cases  where 
such  speeds  are  required.  This  engine  is  presented  as.one  which, 
.distinguished  by  a  system  of  valves  and  valve  movements  per- 
fectly adapted  to  improved  rotative  speed,  has  also  been  designed 
upon  sound  principles,  and  is  made  in  the  most  excellent  manner  ; 
so  that,  without  the  least  drawback,  all  the  advantages  of  this 
speed  may  be  realized  by  the  use  of  it.  A  description  of  this 
engine  naturally  commences  with  the  valve  gear  and  valves. 

Its  central  feature  is  a  link  actuated  by  a  single  eccentric, 
from  which  separate  and  independent  movements  are  given  to  the 
admission  and  the  exhaust  valves. 

Attention  is  first  invited  to 

The  position  of  the  eccentric*  —  The  eccentric  is  placed  on  the 
shaft  in  the  same  position  with  the  crank,  and  cannot  be  altered 
from  this  position.  The  lead  of  the  valves  is  adjusted  by  other 
means.  The  first  requirement  of  this  system  is,  that  the  crank 
and  the  eccentric  shall  have  coincident  movements,  and  so  shall 
arrive  on  their  dead  points,  or  lines  of  centers,  simultaneously. 

To  insure  the  permanence  of  the  eccentric  in  its  correct  posi- 
tion, and  also  for  compactness,  and  as  a  superior  mechanical  con- 


260 


HANDBOOK    ON    ENGINEERING. 


str  action,  it  is  formed  in  one    piece    with  the  shaft,  and  its  low 
side  is  brought  down  to  the  surface  of  it,  as  shown  in  Fig.  1. 

The  link*  —  The  construction  of  the  link  is  also  shown  in 
Fig.  1.  It  is  of  the  form  known  as  stationary  link,  and  con- 
sists of  a  curved  arm,  partly  slotted,  formed  in  one  piece  witli  the 
eccentric  strap,  and  pivoted  at  its  middle  point  on  trunnions,  \yhich 


Fig.    1. 

vibrate  in  an  arc  whose  chord  is  equal  to  the  throw  of  the  eccen- 
tric, about  a  sustaining  pin  secured  rigidly  to  the  bed.  The 
radius  of  the  link  is  equal  to  the  length  of  the  first  rod,  by  which 
its  motion  is  communicated  to  the  admission  valves. 

In  the  slot  is  fitted  a  block  from  which  the  admission  valves 
receive  their  motion.  This  block  is  moved  by  the  action  of  the 
governor,  which  thus  varies  the  point  of  cut-off.  If  the  center 
of  the  block  is  brought  to  the  center  of  the  trunnions,  the  port  is 
not  opened  at  all,  except  by  the  lead  given  to  the  valves,  and  this 


HANDBOOK    ON    ENGINEERING.  2(U 

opening  is  closed  before  the  piston  has  advanced  a  sensible 
amount.  If,  on  the  other  hand,  the  block  is  brought  to  the  end 
of  the  slot,  as  here  represented,  tha  steam  is  not  cut  off  until  the 
piston  has  reached  about  six-tenths  of  the  stroke,  which  is  the 
limit  of  the  admission. 

The  exhaust  valves  are  driven  from  a  fixed  point  on  the  link, 
and  have,  of  course,  an  invariable  motion.  The  movements  of 
the  link  at  this  point  are  admirably  suited  to  this  function,  caus- 
ing the  steam,  wherever  it  may  have  been  cut  off  by  the  admis- 
sion valves,  to  be  held  until  near  the  termination  of  the  stroke, 
when  it  receives  a  free  and  ample  release,  and  is  con  lined  again 
near  the  end  of  the  stroke  by  the  closing  of  the  exhaust  valves  at 
a  point  which  provides  the  compression  required  to  arrest  the 
motion  of  the  reciprocating  parts,  and  at  the  same  time,  fill  the 
end  clearance  of  the  cylinder  with  the  compressed  steam. 

The  peculiar  motion  of  the  link  is  given  to  it  by  a  combination 
of  the  horizontal  and  the  vertical  throws  of  the  eccentric.  The 
horizontal  throw  alone  only  moves  the  link  from  one  to  the  other 
of  the  lead  lines,  which  motion  only  draws  off  the  lap  of  the 
valves.  The  opening  movement  is  produced  by  the  tipping  of  the 
link  alternately  in  the  opposite  directions  beyond  the  lead  lines, 
and  these  tipping  motions  are  given  by  the  vertical  throws  of  the 
eccentric.  Its  upward  throw  tips  the  link  in  the  direction  from 
the  shaft  and  opens  the  port  at  the  further  end  of  the  cylinder ; 
and  its  downward  throw  tips  the  link  towards  the  shaft,  and 
opens  the  port  at  the  crank  end  of  the  cylinder.  At  the  same 
time,  its  horizontal  throw  is  drawing  the  valve  back,  and  when  in 
this  return  movement,  that  point  in  the  link  at  which  the  block 
stands,  crosses  the  head-line,  the  steam  is  cut  off. 

This  link  possesses  a  distinguishing  excellence,  which  will 
now  be  described*  —  The  angular  vibration  of  the  connecting  rod 
causes  a  considerable  difference  in  the  motion  of  the  piston  in 
the  opposite  ends  of  the  cylinder,  retarding  it  in  the  end 


262  HANDBOOK    ON    ENGINEERING. 

nearest  to  the  crank,  and  accelerating  it  at  the  end  farthest  from 
it.  When  the  length  of  the  connecting  rod  equals  six  cranks,  as 
is  usually  the  case,  this  difference  in  velocity  averages  20  per 
cent,  and  at  the  commencement  and  termination  of  the  strokes, 
reaches  the  great  amount  of  forty  per  cent. 

The  driven  arm  of  the  link  is  of  such  length  that  its  angular 
vibration  coincides  in  degree,  as  well  as  in  time,  with  those  of 
the  connecting  rod  ;  and  so  the  trunnions  of  the  link  receive  a 
motion  coincident  with  that  of  the  piston,  and  the  link  gives  to 
the  valves,  in  opening  and  closing  their  ports,  different  velocities, 
accelerated  at  one  end  of  the  cylinder  and  retarded  at  the 
other,  corresponding  to  the  difference  in  the  velocity  of  the 
piston. 

Difference  of  lead*  —  The  application  of  this  gear  to  the 
engine  under  an  adjustment  provides  for  a  slight  difference  in 
lead  at  either  end  of  the  stroke,  and  the  amount  of  this  dissimi- 
larity is  in  the  direct  ratio  as  the  variation  of  the  piston  velocities 
at  the  end  of  the  stroke. 

The  manner  in  which  the  link  imparts  to  the  exhaust 
valves  their  movements*  —  The  exhaust  valves  open  and  close 
their  ports  in  such  manner  that  the  opening  is  made  while  the 
valve  is  moving  swiftly,  and  one-half  of  the  opening  movement 
has  been  accomplished  when  the  piston  arrives  at  the  end  of  its 
stroke.  The  valves  are  so  constructed  that  this  portion  of  the 
movement  opens  the  whole  area  of  the  port,  which  does  not  begin 
to  be  contracted  again  until  the  center  line  of  the  link  has  re- 
crossed  the  lead  lines  on  its  return.  The  speed  of  the  piston  is 
then  also  diminishing,  and  the  exhaust  is  not  throttled  at  all 
until  the  port  is  just  about  to  be  closed. 

The  differential  valve  movement*  —  A  wrist  motion  is  intro- 
duced into  the  connection  of  the  admission  valves. 

In  this  movement,  an  arm  which  is  connected  by  a  rod  with 
the  block  in  the  link,  communicates  through  a  rock  shaft,  motion 


HANDBOOK    ON    ENGINEERING.  263 

to  the  two  other  arms,  causing  them  to  vibrate  in  the  same  verti- 
cal plane  in  which  the  valves  move.  Each  of  these  arms  alter- 
nately rises  nearly  to  the  vertical  position,  while  the  other,  at  the 
same  time,  descends  to  and  beyond  its  dead  point. 

Each  by  a  separate  connection,  imparts  motion  to  one  of  the 
dmission  valves,  and  at  the  top  of  its  vibration  causes  it  to  open- 
and  close  its  port  swiftly  and  then,  descending  to  its  idle  arc, 
reduces  the  motion  of  the  valve  to  an  interval  practically  of  rest. 

These  movements  can  be  followed  in  the  cut  where  the  upper 
arm  is  about  to  move  in  its  arc  to  the  left,  and  thus,  through  the 
lower  connections,  to  open  the  port  at  the  further  end  of  *the 
cylinder,  while  the  lower  arm  will  be  scarcely  moving  in  its  valves 
at  all.  In  this  manner,  the  width  of  opening  is  largely  in- 
creased, chiefly  by  a  difference  in  the  length  of  the  levers,  while, 
at  the  same  time,  fully  one-half  of  the  lap,  or  the  useless  motion 
of  each  valve  after  it  has  covered  its  port,  is  got  rid  of,  so  that 
smaller  valves  and  narrower  seats  are  employed,  and  notwith- 
standing the  greater  opening  movement,  the  total  motion  of  the 
valves  is  very  much  reduced. 

THE  ADJUSTABLE  PRESSURE  PLATES. 

Description  01  these  plates*  —  The  construction  of  these  pres- 
sure plates  and  the  method  of  adjusting  them  are  fully  represented 
in  the  sections  of  the  cylinder,  Figs.  2  and  3. 

On  the  lower  side  of  the  horizontal  section,  Fig.  2,  both 
admission  valves  are  shown,  working  between  their  opposite 
parallel  seats,  one  of  which  is  formed  on  the  cylinder,  and  the 
other  on  the  pressure  plates,  the  latter  having  cavities  opposite 
the  ports. 

The  valve  at  the  further  end  of  the  cylinder  is  at  the 
extremity  of  its  lap,  while  the  one  at  the  crank  end  has  com- 
menced to  open  the  four  passages  for  admission  of  the  steam. 


264 


HANDBOOK    ON    ENGINEERING. 


The  vertical  cross-section,  Fig.  3,  passes  through  the  middle 
of  one  pressure  plate  and  shows  its  form  and  the  means 
employed  for  its  adjustment.  It  is  made  hollow  and  most  of 


Fig.  2. 

the  steam  supplied  to  two  of  the  openings  passes  through  it. 
It  is  arched  to  resist  the  pressure  of  the  steam  without  deflec- 
tion. It  rests  on  two  inclined  supports,  one  above  and  the 
other  below  the  valve.  These  inclines  are  steep,  so  .that  the 
plate  will  be  sure  to  move  freely  down  them  under  the  steam 
pressure,  and  also  that  it  may  be  closed  up  to  the  valve  with 
only  a  small  vertical  movement.  It  is  prevented  from  moving 
down  these  inclines  by  a  screw,  passing  through  the  bottom 
of  the  chest,  the  point  of  which,  as  also  the  plug  against  which 
it  bears,  is  of  hardened  steel. 

The  pressure  plate  is  held  in  its  correct  position  by  projections 
in  the  che-«t,  on  one  side,  and  tongues  projecting  from  the  cover 
on  the  other,  which  bear  against  it  near  each  end,  as  shown. 


HANDBOOK    ON    ENGINEERING. 


265 


Between  these  guides,  it  is  capable  of  motion  up  and  down  its 
inclined  supports,  and  also  directly  back  and  forth  between  the 
valve  and  the  cover. 

The  pressure  of  steam  is  always  on  this  plate,  and  tends  to 
force  it  down  the  incline  to  rest  on  the  valve.  By  means  of 
the  screw  it  is  forced  against  the  steam  pressure,  up  the  in- 
clines and  away  from  the  valve.  This  adjustment  is  capable  of 
great  precision,  so  that  the  valve  works  with  entire  freedom 
between  its  opposite  seats,  and  still  is  steam-tight. 

How  these  plates  act  as  relief  valves,  —  Whenever  the  pres- 
sure in  the  cylinder  exceeds  that  in  the  chest,  the  admission 


pressure  plate  is  instantly  moved  back  to  contact  with  the  cover, 
thus  affording  an  ample  passage  for  the  discharge  of  water 
before  it  can  exert  a  dangerous  strain.  This  plate  is  superior 


266 


HANDBOOK    ON    ENGINEERING. 


in  this  action  to  any  of  the  ordinary  forms  of  relief  valve,  both 
in  the  area  opened,  and  also  in  being  self -adjusted  to  the  pressure, 
and  opening  fully  the  instant  that  is  exceeded. 

How  to   keep   the  admission   valves  tight*  —  These  valves, 
though  moving  in  complete  equilibrium,  are  liable  to  slight  wear. 


This  should  be  taken  up  as  it  appears,  by  letting  down  the 
pressure  plates.  The  construction  of  these  plates  and  the  method 
of  adjusting  them,  are  shown  in  the  accompanying  sections,  made 
through  the  steam  chest  at  one  end  of  the  cylinder.  Of  these, 
Figs.  1  and  2  are  horizontal  sections,  showing  the  four-opening  of 


HANDBOOK    ON    ENGINEERING. 


267 


the  valve —  first,  when  commencing  to  open,  with  arrows  indicating 
the  course  of  the  steam  ;  and,  second,  at  the  extreme  point  of  its 
lap;  while  Figs.  3  and  4  are  vertical  sections,  showing  the 


m 


pressure  plate  —  first,  when  by  turning  the  bolt  d  forward  it  is 
forced  up  the  inclines  and  away  from  the  valve,  producing  aleak  ; 
and  second,  when  it  is  let  down  to  its  proper  working  position. 
A  is  the  port,  B  the  valve,  and  C  the  pressure  plate.  The  latter 


is  made  with  a  trussed-back  and  so  cannot  be  deflected  by  the 
steam  pressure.  Through  the  passage  thus  formed,  the  steam 
reaches  two  of  the  openings. 


268  HANDBOOK    ON    ENGINEERING. 

The  pressure  plate  rests  on  two  inclined  supports,  <•,  <•,  and 
the  pressure  of  the  steam  forces  it  down  these  inclines  us  far 
as  the  bolt  d  underneath  will  allow.  This  bolt  holds  the  plate 
just  off  from  the  valve,  so  that  the  latter  moves  freely, 
and  is  still  steam  tight.  Whenever  leakage  appears,  a  minute 
turning  of  this  bolt  backwards  lets  the  pressure  plate  down  and 
closes  it. 

Provision  is  made  for  readily  detecting  the  least  leakage,  as 
follows:  When  the  engine  is  warmed  up  in  its  normal  working 
condition,  open  the  indicator  cocks,  or  in  the  absence  of  these, 
remove  the  plugs  from  the  top  of  the  cylinder,  unhook  the  link 
rod,  and  set  the  valves  by  the  starting  bar  so  that  both  ports  are 
covered,  and  turn  on  the  steam.  If  the  valve  leaks  at  the  end  of 
the  cylinder,  which  is  not  then  open  to  the  atmosphere  or  the 
condenser,  the  steam  will  blow  out  at  the  opening  provided,  having 
no  other  outlet.  Then  let  down  its  pressure  plate  by  backing  the 
bolt  very  carefully  till  the  leak  disappears.  The  valve  should 
still  move  freely  when  the  leak  has  disappeared,  and  the  pressure 
plate  must  not  be  let  down  any  closer  than  is  necessary  for  this 
purpose. 

Leakage  at  the  opposite  end  of  the  cylinder  will  not  generally 
be  seen,  the  steam  escaping  freely  by  the  open  exhaust.  To  test 
its  valve  in  the  same  manner,  the  engine  must  be  turned  on  to  the 
opposite  stroke.  These  examinations  should  be  made  from  time 
to  time. 

In  the  small  engines  which  have  no  starting  bar,  the  valve  rod 
can  be  disconnected  and  moved  by  hand  to  test  this  point. 

An  engine  should  never  be  started  till  it  is  warmed  up.  The 
valves  warm  quicker  than  the  supports  on  which  the  pressure 
plates  rest,  and  are  tight  between  their  seats  by  expansion,  until 
the  temperatures  have  become  nearly  equalized.  Provision  for 
detecting  and  stopping  any  leak  of  steam  is  the  crowning 
excellence  of  this  valve. 


HANDBOOK    ON    ENGINEERING.  269 

These  valves  are  small  and  light ;  each  admits  and  cuts  off 
the  steam  simultaneously  at  four  openings ;  each  works  in  com- 
plete equilibrium ;  their  line  of  draft  is  central,  so  that  unequal 
wear  is  entirely  avoided. 

To  set  the  admission  valves*  —  Place  the  engine  on  one  of  its 
dead  centers  as  explained  on  page  195.  Then  raise  the  governor, 
bringing  the  center  of  the  block  between  the  centers  of  the 
trunnions  of  the  link. 

With  the  governor  remaining  up,  set  the  valve  that  is  about 
to  open,  giving  to  it  a  lead  of  from  T^"  to  T3^",  according  to 
the  size  of  the  engine.  High  speed  requires  considerable  lead. 
Repeat  this  for  the  other  valve  on  the  opposite  center. 

On  letting1  the  governor  down,  the  crank  remaining  on  the 
dead  center,  it  will  be  seen  that  the  valve  is  moved  a  short  dis- 
tance. This  motion  of  the  valve,  produced  by  moving  the  block 
from  the  trunnions  to  the  extremity  of  the  link  while  the  crank 
stands  on  the  center,  is  the  same  in  amount  on  either  center  and 
takes  place  in  the  same  direction ;  namely,  towards  the  crank. 
Its  effect  is,  therefore,  to  cover  the  port  nearest  the  crank  and  to 
enlarge  the  opening  of  the  port  farthest  from  it ;  so  that  the  lead, 
which  is  equal  at  the  earliest  point  of  cut  off,  is  at  the  crank  end 
of  the  cylinder  gradually  diminished,  and  at  the  back  end  increased 
in  the  same  degree  as  the  steam  follows  further. 

The  effect  of  this  is  to  equalize  the  opening  and  cut-off  move- 
ments, so  that,  on  setting  the  governor  at  any  elevation  whatever 
and  turning  the  engine  over,  the  openings  made  and  the  points  of 
cut-off  will  be  found  to  be  identical  on  the  opposite  strokes,  from 
the  commencement  up  to  the  maximum  admis'sion.  This  differ- 
ence in  the  lead  is  also  singularly  adapted  to  the  difference  in  the 
piston  velocity  at  the  two  ends  of  the  cylinder. 

In  case  the  indicator  shows  that  the  lead  of  either  admission 
valve  requires  to  be  changed,  this  is  done  without  opening  the 
chest,  by  lengthening  or  shortening .  the  stem  at  the  socket  of 


270  HANDBOOK   OX    ENGINEERING. 

its  guide,  bearing  in  mind  that  each  valve  moves  towards  the 
middle  of  the  cyclinder  to  open  its  port. 

To  set  the  exhaust  valves.  —  These  have  an  invariable  motion, 
and  are  admirably  adapted  to  their  purpose.  They  are  set  so  as 
to  open  before  the  end  of  the  stroke  enough  to  give  ample  lead, 
and  close  again  when  the  piston  is  on  the  return  stroke,  early 
enough  to  effect  the  required  compression. 

All  the  valves  are  held  between  pairs  of  brass  nuts,  of  which 
the  inner  one  is  flanged.  These  nuts  must  be  securely  locked, 
and  should  be  so  set  upon  the  valve  that  it  is  free  to  adjust  itself 
between  the  nuts  while  yet  sufficiently  tight  that  no  ' '  lost  motion  ' ' 
exists.  To  avoid  the  consequences  of  a  mistake,  care  should  be 
taken,  before  closing  the  valve  chests,  to  turn  the  engine  slowly 
through  an  entire  revolution,  while  the  movements  of  the  valves 
are  carefully  watched,  so  as  to  insure  that  they  have  not  been  BO 
set  as  to  bring  the  valves  or  their  nuts  into  contact  with  the  ends 
of  the  chest  at  the  extremes  of  their  movements. 

The  governor*  —  The  Porter  Governor,  original  in  its  type, 
stands  unexcelled  as  adapted  to  stationary  engines,  requiring  close 
regulation.  The  active  parts  are  very  light,  the  power  being- 
derived  from  a  high  rotative  speed,  causing  a  sensitiveness  in  its 
movements  that  will  arrest  fluctuations  and  produce  uniformity  in 
the  running  of  the  engine.  It  has  been  so  perfected  that  at  the 
present  day  it  is  easily  adapted  to  the  requirements  of  any  class 
of  work  necessitating  a  governor,  and  is  especially  desirable  for 
an  engine  where  a  steady  speed  is  necessary. 

The  speed  of  this  governor  being  constant,  makes  it  equally 
efficient  upon  an  engine  running  either  at  a  high  or  low  number 
of  revolutions.  That  is  to  say,  the  speed  of  engine  can  be 
altered  from  time  to  time  by  changing  the  governor  pulley,  the 
governor  itself  continuing  to  run  at  the  same  speed  and  under  the 
same  strains,  and  being  stationary,  it  is  always  open  to  observa- 
tion. Whereas,  any  change  in  speed  of  engine  with  the  wheel  or 


HANDBOOK    ON    ENGINEERING.  271 

shaft  governor,  increases  or  decreases  the  initial  strains  upon  all 
the  parts  of  the  governor,  and  they  have  to  be  adjusted  accordingly. 

It  is  manufactured  and  sold  separate  from  the  Porter-Allen 
engines. 

How  to  tighten  the  side  boxes  of  the  main  bearing*  —  This 
is  done  by  drawing  up  the  wedge  with  the  bolts  by  which  it  is 
suspended  from  the  cap.  The  time  to  do  this  is  when  the  engine 
is  running  and  the  freedom  of  the  journal  between  its  side  boxes 
can  be  felt.  The  engineer  can  then  draw  up  the  wedges  to  take 
this  out  as  much  as  he  deems  prudent. 

DIRECTIONS     FOR    SETTING    AND    RUNNING    THE    PORTER- 
ALLEN   STEAM    ENGINE. 

The  foundation,  —  This  should  be  made  of  concrete,  hard 
bricks  or  stone  laid  in  cement.  Bricks  are  preferred  on  account 
of  their  rectangular  form  and  of  the  more  perfect  bond  they 
make  with  the  cement.  Stones  of  irregular  form  are  sure  to  have 
the  cement  bond  broken  and  to  spread  under  the  strain  of  the 
bolts.  The  bricks  should  be  wet,  and  the  cement  washed  into 
every  course. 

Time  should  be  allowed  for  the  cement  to  set  before  any  weight 
is  put  upon  it.  A  week,  at  least,  is  required  for  this  purpose  ;  a 
month  is  none  too  long. 

Heavy  cut  stone  is  ornamental  for  a  coping,  but  not  essential 
where  there  is  a  bed-plate ;  the  bed-plate  of  an  engine  being  not  a 
mere  name,  but  a  reality 

A  foundation  plan  for  locating  the  bolts  should  be  made  for  each 
engine.  The  bolts  should  have  some  play  in  the  masonry.  The 
best  way  of  insuring  this  is  to  inclose  each  bolt  in  a  wooden  box 
of  half -inch  stuff,  about  sixteen  inches  long,  which  is  drawn  up 
as  the  courses  are  added  and  removed  entirely  before  the  engine 
is  placed  on  the  foundation,  so  the  bolt  holes  may  be  poured  full 
of  cement  after  the  setting  is  completed. 


272  HANDBOOK    ON    ENGINEERING. 

Under  ordinary  circumstances,  a  foundation  built  to  the  plan 
furnished  is  ample  to  hold  the  engine  still ;  but  when  it  must  be 
built  on  soft  ground,  or  on  sand  or  loose  gravel,  or  must  be  carried 
up  through  abasement  or  cellar,  it  should  be  extended  at  the  base 
lengthwise  in  each  direction.  Sometimes,  both  these  obstacles  to 
stability  are  met  with,  when  the  foundation  should  be  extended  as 
far  as  practicable,  and  at  one  end,  at  least,  tied  to  a  wall  quite 
up  to  the  engine-room  floor.  The  builders  of  the  engine  should 
be  consulted  in  such  cases. 

Setting  the  bed* — This  setting  is  done  in  the  Usual  manner, 
by  a  line  through  the  cylinder,  which  is  bolted  at  the  end  of  the 
bed  in  alignment  with  the  guides.  In  case  the  cylinder  is  not 
yet  in  place,  it  is  represented  by  the  bore  in  the  head  of  the  bed, 
and  the  line  is  to  be  -continued  midway  between  the  side  rails  of 
the  lower  guide  bars. 

The  guides  lie  in  one  plane  and  are  to  be  used  for  leveling  the 
bed  in  both  directions. 

The  base  of  the  bed  is  not  brought  in  contact  with  the  founda- 
tion. Thin  parallel  packing  pieces  are  to  be  placed  on  each  side 
of  each  bolt  and  under  each  end  of  the  main  bearing,  and  the  bed 
must  bear  equally  on  all  these,  when  the  guides  are  level  in  all 
directions,  before  any  strain  is  put  on  the  bolts.  After  these  have 
been  tightened  and  the  guides  are  finally  found  to  be  level,  the 
broad  flange  of  the  bed  is  brought  to  a  general  bearing  on  the 
foundation,  by  running  sulphur  under  it,  or  by  caulking  with 
iron  borings  wet  with  water  made  only  slightly  acid  with  sal- 
ammoniac. 

Setting  the  shaft.  —  In  placing  the  shaft  in  position,  three 
requirements  must  be  observed.  First,  to  place  it  at  a  right 
angle  with  the  axis  of  the  cylinder.  Second,  that  it  shall  be  level. 
Third,  that  it  lies  fairly  in  its  bearings.  It  is  readily  squared. 
The  crank  disc  is  finished  on  the  shaft  centers  after  the 
pin  has  been  set,  so  that  its  rim  is  on  the  opposite  side  equally 


HANDBOOK    ON    ENGINEERING.  273 

distant  from  its  center  line,  the  shaft  is  square.  It  is  leveled  by 
plumbing  the  crank  disc.  When  thus  set  it  will  lie  fairly  in  the 
main  bearing ;  and  if  the  outer  bearing  has  been  correctly  set,  it 
will  lie  fairly  in  that  also.  This  is  tested  by  rotating  the  shaft 
entirely  dry.  Brightened  rings  will  show  what  parts  of  the 
journals  have  found  bearings,  and  on  lifting  the  shaft,  bright 
spots  on  the  babbitt  metal  will  show  where  these  bearings  were. 

The  boxes  are  slightly  larger  than  the  journals  and  so  the  lat- 
ter should  bear  along  the  center  of  the  lower  box  and  not  on  the 
sides. 

The  journals  of  the  shaft  if  set  as  here  directed  will,  with 
ordinary  lubrication,  run  cold  from  the  start.  Should  the  shaft 
ever  get  out  of  line,  it  may  be  squared  by  gauging  between  the 
rim  of  the  crank  disc  and  bosses  provided  on  the  bed. 

SPECIFICATIONS   FOR   CENTRALLY  BALANCED   CENTRA 
FUQAL  INERTIA  GOVERNOR. 

It  is  difficult  to  say  just  what  fs  the  most  important  part  of 
a  modern  steam  engine,  but  certainly  its  governor  is  among  the 
very  first.  Here  then  is  my  idea  of  what  they  should  be :  — 

First.  The  governor  must  so  regulate  the  speed  of  the  engine's 
revolutions  that  when  starting  or  stopping  it  shall  not  "  pound  " 
or  knock,  which  means  some  danger,  considerable  wear  and  much 
annoyance. 

Second.  It  must  so  regulate  the  engine's  speed  when  in  service, 
that  when  125  per  cent  of  its  rated  capacity  be  instantly  thrown 
upon  the  engine,  the  change  in  speed  will  not  be  more  than  1 J  per 
cent  greater  or  less  than  the  constant  speed ;  and  that  if  the  same 
load  be  instantly  thrown  off  the  engine,  the  variation  shall,  in  that 
case,  be  no  greater  than  one  per  cent. 

Third.  That  the  governor  must  show  every  evidence  of  stability 
or  ability  to  have  all  descriptions  of  break  loads  thrown  on  or  off, 

18 


274  HANDBOOK    ON    ENGINEERING. 

or  both,  without  "  racing  "  or  "  weaving  "  beyond  1^  per  cent  of 
constant  speed.  This  is  to  insure  against  accident  and  expert 
assistance. 

Fourth.  Should  any  part  of  the  governor  or  its  attachments 
break  or  become  disconnected,  the  device  must  not  do  otherwise 
than  to  bring  the  engine  to  a  full  stop. 

Fifth.  All  the  parts  of  the  governor  must  be  light,  yet  of  finest 
materials,  to  save  wasted  energy  and  yet  insure  reliability. 

Sixth.  The  construction  must  be  such  that  during  all  ranges  of 
cut-off,  the  parts  shall  remain  at  all  times  in  perfect  balance. 
44  Out-of -balance  "  almost  more  than  any  other  one  dilliculty 
has  prevented  the  full  success  of  wheel  governing  engines,  there- 
fore, this  feature  must  be  eliminated.  No  device  obviously  inca- 
pable of  constant  balance  should  be  considered  unless  that  long 
sought  and  potential  factor  of  fine  running  is  to  be  sacrificed  with 
open  eyes. 

Seventh.  All  parts  subjected  to  transmitting  strains  must  be  of 
steel. 

Eighth.  All  transmitting  •  bearings  must  be  provided  with 
hardened  and  ground  to  gauge  steel  pins,  each  of  which  must  ce 
furnished  with  movable  phosphor  bronze  bushings  to  save  wear 
and  enable  quick  and  interchangeable  repairs. 

Ninth.  Springs  must  be  of  best  quality  and  made  with  screwed 
"plug"  connections.  The  bending  of  the  spring  into  hook  or 
eye  for  connecting  will  not  be  permitted. 

Tenth.  Governor  must  be  so  designed  and  provided  with  mov- 
able weights,  that  the  speed  may  be  diminished  or  increased 
graduated  amounts  without  disturbing  otherwise  the  adjustment 
of  the  mechanism. 

Eleventh.  Any  governor  so  designed  as  to  accomplish  regula- 
tion clause  primarily,  and  at  the  same  time  fulfills  all  other 
requirements  will  naturally  receive  preference  over  other  devices, 
which  evidently  fairly  accomplish  regulation  but  fail  in  other 


HANDBOOK    ON    ENGINEERING. 


275 


expectations,  and  yet  apparently  have  only  lower  first  cost  as  a 
defense. 

The  Armington  and  Sims  Engine,  as  is  well  known,  is  of  the 
high  speed  type,  and  in  its  earlier  form  was  designed  with  double 
eccentrics,  one  inside  of  the  other.  These  eccentrics  are  operated 
by  the  shaft  governor,  and  the  compound  motion  produced  by  the 
movements  of  the  two  eccentrics  is  such  that  the  valve  has  equal 
lead  for  all  points  of  cut-off. 


Valve  Gear  of  the  Armington  &  Sims  Automatic  Engine. 

The  method  of  setting  the  valve  is  very  simple,  for  all  engines 
of  this  make  are  sent  out  with  the  valve  stem  and  slide  marked  at 
points  C  and  I?  in  the  sketch,  and  these  points  should  be  set  just 
three  inches  apart.  The  following  are  the  directions  which  the 
builders  supply :  — 

"  If  the  distance  between  J3  and  C  is  just  three  inches  you  will 
know  that  the  valve  is  all  right.  If,  however,  you  wish  to  put  in 
a  new  valve  and  adjust,  then  remove  the  steam-chest  cover  and 
place  the  engine  on  the  center  as  follows :  Place  line  marked  A, 
which  is  on  the  crank  pin  side,  with  line  on  opposite  side  of  rim 
marked  F  (not  shown  in  drawing),  level  with  engine;  now  take 
out,  or  loosen  up  the  springs  and  block  the  weights  out  so  that 
the  distance  betwee^weights  and  pin  at  D  E  will  be  J  of  an  inch ; 
adjust  the  valve-stem  at  the  guide  so  that  by  turning  the  engine  over 


276  HANDBOOK    ON    ENGINEERING. 

from  one  center  to  the  other  the  lead  will  be  the  same  at  both 
ports ;  then  make  a  new  mark  distinctly  on  the  valve-rod,  so  that 
the  distance  B  C  will  be  the  standard  three  inches. 

"  It  is  not  possible  to  reverse  the  direction  of  running  without 
sending  to  the  factory  for  new  parts.  The  governor  is  not  con- 
structed so  that  one  set  of  parts  can  be  used  for  running  both 
ways." 

THE  CARE  AND   MANAGEMENT    OF    HARRISBURQ  ENGINES. 

It  is  essential  to  the  successful  operation  of  any  high-class  and 
expensive  machinery,  that  the  person  in  charge  be  gifted  with  a 
fair  degree  of  intelligence  and  alertness,  and  while  I  have  at- 
tempted to  formulate  a  few  rules  as  a  guide  to  the  person  in 


Sectional  Elevation  of  Harrisburg  Standard  Four-Valve 
Tandem  Compound  Engine. 

charge  of  an  engine,  the  fact  must  not  be  overlooked  that  a  great 
deal  depends  upon  the  skill  and  judgment  of  the  operator  himself, 
and  that  it  is  manifestly  impossible  to  give  rules  other  than  of  a 
general  character  and  which  may  frequently  have  to  be  modified 
to  suit  the  different  conditions  that  may  arise.  However,  the 


HANDBOOK    ON    ENGINEERING.  277 

following  aiv  some  suggestions  for  the  convenience  of  operating 
engineers :  — 

When  engines  of  these  styles  have  been  properly  erected,  the 
steam,  exhaust  and  drain  connections  completed,  and  the  piston 
and  valve  rods  packed,  the  operator  should  be  careful  to  see  that 
all  parts  are  in  proper  position  and  firmly  secured. 

The  bed  should  be  thoroughly  cleansed  inside  and  a  good 
quality  of  machine  oil  poured  into  the  reservoir  beneath  the  crank, 
until  it  is  just  in  contact  with  the  crank  disc. 

A  mineral  oil  only  should  be  used,  and  of  medium  viscosity. 
Fill  the  eccentric  lubricating  cup  and  flush  the  main  bearings 
with  the  oil. 

The  cylinder  lubricator  should  be  filled  with  a  first-class  qual- 
ity of  cylinder  oil,  of  heavy  body. 

The  best  oils  obtainable  are  the  most  economical,  without 
question. 

Careful  preparations  before  starting1  engine*  —  The  cylinder 
and  steam  chest  drain  valve  should  now  be  opened,  and  the 
throttle  valve  carefully  started  just  enough  to  allow  a  small  quan- 
tity of  steam  to  flow  through  the  cylinder  and  out  through  the 
drain  pipes,  but  not  enough  to  actually  start  the  engine  in 
motion. 

After  the  cylinder  and  valves  have  been  thoroughly  heated 
and  any  water  standing  in  the  steam  pipes  thus  blown  off,  start 
the  oil  flowing  in  the  cylinder  lubricator  cup.  A  general  survey 
of  the  engine  should  now  be  taken  and  if  everything  is  found  to 
be  in  proper  condition,  carefully  open  the  throttle  valve  and  bring 
the  engine  gradually  up  to  speed,  when  it  should  be  noted  that 
the  governor  is  controlling  the  machine.  Examine  the  bearings 
and  eccentric  to  see  if  the  oil  is  flowing  properly,  and  make  sure 
that  every  part  is  operating  smoothly,  after  which  the  drain  valves 
may  be  closed. 

Adjustments  for  weaiv  —  When  the  engine  has  been  in  opera- 


278  HANDBOOK    ON    ENGINEERING. 

tion  long  enough  to  necessitate  the  adjustment  of  the  working 
parts,  care  should  be  used  to  avoid  adjusting  them  so  close  as  to 
cause  heating,  and  the  following  general  rules  should  be 
observed :  — 

The  caps  on  the  main  bearings  should  always  have  sufficient 
liners  underneath  to  enable  the  nuts  on  the  bearing  studs  to  draw 
the  cap  down  solidly  upon  them  and  not  pinch  .the  shaft,  which 
should  be  free  to  revolve  in  its  bearings  without  unnecessary  play. 

Adjustment  of  crank-end  connecting;  rod*  —  In  adjusting  the 
connecting-rod  box  at  the  crank  pin  end  the  same  general  rules 
should  be  observed  regarding  the  liners  under  the  cap,  the  large 
nuts  drawn  solidly  upon  it,  the  small  nuts  firmly  jammed,  and 
the  cotter  pins  placed  in  position. 

The  adjustment  of  the  box  should  then  be  tested  with  a  lever 
about  12  inches  in  length,  the  adjustment  being  so  made  that 
with  a  lever  of  this  length  the  operator  can  easily  move  the  end  of 
the  connecting  rod  sufficiently  to  take  up  the  side  play  between 
the  flanges  on  the  crank  pin  and  the  ends  of  the  box.  The 
adjustment  should  never  be  made  so  close  that  this  side  movement 
cannot  be  observed. 

Adjustment  of  cross-head  pin  box,  —  The  adjustment  of  the 
connecting-rod  box  at  the  cross-head  pin  end  should  be  made  by 
removing  the  name  plate  from  the  engine  frame  and  placing  the 
crank  on  the  center  nearest  the  cylinder,  then  with  the  wrench 
provided  for  that  purpose,  slack  off  both  wedge  screws  at  the 
upper  and  lower  sides  of  the  connecting  rod,  and  draw  the  wedge 
up  until  it  is  solid  against  the  box,  then  slack  off  that  screw 
about  a  sixth  of  a  turn  and  draw  up  the  other  so  as  to  firmly  lock 
the  wedge ;  this  method  prevents  the  box  from  pinching  the 
cross-head  pin. 

The  "  flats n  on  the  cross-head  pin  should  always  be  at  the 
top  and  bottom  to  avoid  wearing  a  shoulder,  and  the  nut  on  the 
end  should  be  drawn  up  firmly,  but  not  so  much  as  to  spring  the 


HANDBOOK    ON    ENGINEERING.  279 

bosses  of  the  cross-head  together,  nor  yet  enough  to  make  the 
box  tight  on  the  ends. 

I  prefer  adjustment  of  the  cross-head  in  the  guides  made  by 
liners  of  paper  or  tin,  placed  between  the  bronze  shoes  and  the 
body  of  the  cross-head. 

Adjustment  of  cross-head  shoes*  —  In  order  to  do  this  it  is 
necessary  to  remove  the  pin  and  the  end  of  the  connecting  rod 
from  the  cross-head,  and  with  a  wooden  lever  placed  in  the  pin 
hole  turn  the  cross-head  until  the  shoes  are  out  of  the  guides, 
then  remove  the  shoes  and  place  the  liners  beneath  them.  Care 
should  be  used  that  the  cross-head  does  not  fit  the  guides  too 
closely ,  and  that  it  can  be  moved  freely  with  a  short  lever  from 
one  end  of  the  guides  to  the  other,  while  disconnected  from  the 
connecting-rod. 

The  cross-head  should  never  be  run  very  close  and  should 
always  be  free  enough  to  allow  long  and  continuous  runs  without 
causing  the  top  of  the  bed  over  the  guides  to  feel  uncomfortably 
warm  to  the  touch. 

Attachment  of  cross-head  to  piston  rod*  —  When  making  any 
adjustments  of  the  cross-head,  it  is  well  for  the  operator  to  assure 
himself  that  the  lock  nut,  which  prevents  the  piston  rod  from 
turning  in  the  boss  at  the  end  of  the  cross-head,  is  securely  in  place. 
All  but  the  largest  Harrisburg  engines  are  tested  under  steam 
before  leaving  the  works,  and  the  valves  set  with  the  indicator. 

The  distance  from  the  cylinder  head  end  of  the  valve,  when 
the  crank  is  on  the  center  nearest  the  cylinder,  is  marked  on  the 
end  of  the  cylinder  directly  underneath  the  steam  chest  cover. 
If  from  any  cause  the  valve  should  become  deranged,  place  the 
crank  on  the  center  described  and  with  a  scale  or  rule,  see  that 
the  valve  position  corresponds  to  the  dimension  marked  on  the 
end  of  the  cylinder;  and  if  out  of  position,  it  can  easily  be  re- 
adjusted by  means  of  the  device  provided  for  that  purpose,  at  the 
outer  end  of  the  valve  stem. 


280  HANDBOOK    ON    ENGINEERING. 

On  the  Harrisburg  Ideal  Engines,  where  the  bull  joint  con- 
nection is  used  between  the  valve  stem  and  the  eccentric  rod,  the 
wear  is  followed  up  by  filing  the  end  of  the  bronze  connection 
that  the  cap  is  screwed  against,  which  holds  the  ball  in  place. 
And  on  the  Harrisburg  Standard  Engines,  where  the  ram  box 
connection  is  used,  the  adjustment  is  made  by  filing  the  half  of 
the  bronze  box,  which  is  attached  to  the  end  of  the  eccentric  rod 
that  connects  with  the  ram. 

Adjustment  of  eccentric  strap.  —  The  eccentric  strap  adjust 
ment  is  made  by  liners  placed  between  the  halves  of  the  strap  and 
double  nutted  bolts.  When  adjustment  is  necessary,  the  other 
end  of  the  eccentric  rod  should  be  disconnected  and  after  drawing 
up  the  strap  bolts  it  should  be  tested  by  giving  the  strap  a  half 
revolution  about  the  eccentric.  If  it  is  found  that  the  friction 
between  the  strap  and  eccentric  is  sufficient  to  support  the  weight 
of  the  rod,  the  bolts  should  be  loosened  until  the  strap  moves 
freely  without  lost  motion.  The  double  nuts  should  then  be 
locked  and  the  cotter-pins  replaced  in  the  ends  of  the  bolts. 

How  to  alter  engine  speed.  —  The  governor  used  on  all  Har- 
risburg Engines  is  the  Centrally  Balanced  Centrifugal  Inertia 
Type.  A  few  words  of  explanation  may  be  of  service  to  oper- 
ating engineers. 

The  weight  arms  are  constructed  with  differential  weight 
pockets,  to  allow  of  a  considerable  range  of  speed  adjustment 
without  altering  the  tension  of  the  springs.  If  an  increase  in 
speed  is  desired,  remove  weights  of  an  equal  thickness  from  the 
weight  pockets  of  the  levers,  and  add  weights  of  an  equal  thick- 
ness to  obtain  a  decrease  in  speed.  If  an  increased  speed 
causes  the  governor  to  "  race  "  or  "  weave,"  move  the  clamp  in 
the  slot,  to  which  the  outer  end  of  the  spring  is  attached,  farther 
from  the  small  end  of  the  weight  lever.  If  this  does  not  entirely 
correct  this  sensitive  condition,  screw  the  plug  into  the  spring 
until  the  racing  ceases.  If  the  decrease  of  speed  so  obtained 
renders  the  governor  too  sluggish  in  action,  move  the  clamp  in  the 


HANDBOOK    ON    ENGINEERING.  281 

slot  in  the  opposite  direction.  If  this  does  not  improve  the  regu- 
lation, and  the  speed  is  lower  than  desired,  add  weights  of  an 
even  thickness,  increasing  the  spring  tension  until  the  proper 
speed  is  obtained.  The  main  lever  bearings  which  are  equipped 
with  anti-friction  steel  rollers,  should  be  oiled  about  once  a  week, 
and  taken  out  and  cleaned  about  once  a  month ;  the  other  joints 
fitted  with  compression  grease  cups,  should  be  treated  in  the  same 
manner.  About  once  a  month,  also,  the  springs  should  be  dis- 
connected and  the  governor  and  valve  gear  tested  by  hand,  to  make 
sure  all  joints  are  working  freely. 

The  foregoing  will  apply  also  to  the  Harrisburg  Standard  and 
Ideal  Compound  Engines,  and,  in  general,  to  the  Harrisburg  Self- 
Oiling  Four  Valve  Engines.  Adjustment  for  wear  in  the  valve 
gear  connection  of  the  latter  type  of  engines  is  obtained  by  filing 
the  halves  of  the  bronze  boxes  on  the  ends  of  the  rods  connecting 
the  valves  with  the  wrist  plates  and  rocker  arms,  and  on  the 
wrist  plate  and  rocker  arm  pins,  by  means  of  bronze  shoes  let 
into  the  sides  of  the  bearings,  the  wear  being  followed  up  by  the 
screws  provided  with  lock-nuts,  and  all  bearings  lubricated  by 
means  of  compression  grease  cups.  The  Harrisburg  Corliss  En- 
gines,of  the  larger  sizes,  are  provided  with  quarter  boxes  in  the 
main  bearings  with  wedge  and  screw  adjustment,  and  are  built  self- 
oiling  or  otherwise,  according  to  size.  The  lubrication  of  the  prin- 
cipal bearings  is  accomplished  by  means  of  oil  cups,  and  the  valve- 
gear  connections  by  means  of  conveniently  arranged  grease  cups- 

McINTOSH    AND   SEYflOUR   HIGH    SPEED    ENGINE. 

How  to  set  the  valve*  —  When  the  engine  is  sent  out  from 
the  shop,  the  valves  are  set  and  trammed  with  three  inch  tram 
from  the  valve-rod  to  the  valve-rod  slide  at  C  />,  and  from  the 
eccentric  rod  to  the  eccentric  rod  head  at  E  F,  on  the  valve-slide 
end,  and  a  tram  is  furnished  with  the  engine,  or  a  new  tram  can 
be  made  with  exactly  three  inches  distance  between  the  points, 
which  will  suffice. 


282 


HANDBOOK    ON    ENGINEERING. 


In  case  the  tram  marks  become  lost,  or,  owing  to  wear  of 
the  valve  gear,  the  length  of  connection  is  altered,  the  proper 
procedure  is  to  put  the  engine  on  one  center,  and  then  on  the 


A  Sectional  Cut  of  Mclntosh  and  Seymour  High-Speed  Engine, 
Showing  -Valve  and  Governor. 

other,  and  observe  the  leads  which  occur  when  the  governor  is  in 
the  normal  position  of  rest,  as  shown.  The  lead  on  the  crank  end 
should  be  three  times  as  much  as  the  lead  on  the  head  end,  if  the 
connection  between  the  valve  and  eccentric  is  of  proper  length. 

When  the  valve  is  set  this  way,  the  cut-off  on  the  two  ends 
of  the  cylinder  will  be  approximately  equal  at  one-quarter  cut-off 
on  the  smaller  size  engines  having  inside  governors. 

Preliminary  to  adjusting  connections  between  the  valve  and 
eccentric,  care  should  be  taken  that  the  mark  on  eccentric  G  H, 
corresponds  to  the  mark  on  the  pendulum. 

In  examining  the  steam  leads,  as  described  above,  it  should 
be  noted  that  the  surface  B  on  the  valve  has  nothing  to  do  with 
the  steam  distribution,  but  it  is  merely  to  give  ample  wearing  sur- 
face, and  that  the  steam  is  admitted  to  the  cylinder  through  the 
port  which  is  between  B  and  the  steam  edge  which  is  at  A,  and 
the  lead  should  be  measured  between  this  steam  edge  and  the 


HANDBOOK    ON    ENGINEERING. 


283 


of  the  port  leading  to  the  cylinder.  On  engines  of  larger 
size  having  outside  governors,  a  similar  method  should  be  em- 
ployed in  setting  the  valves,  except  that  the  trams  are  four  inches 
from  point  to  point,  and  should  be  used  between  the  valve-rod 
slide  and  valve-rod,  and  the  eccentric  rod  and  the  eccentric 
rod  head  at  governor  end,  instead  of  slide  end,  as  above. 


INSTRUCTIONS    FOR    STARTING   AND   OPERATING    IDEAL 

ENGINES. 

Before  starting-  engine*  —  Open  cylinder  cocks  and  throttle 
valves  sufficiently  to  warm  the  cylinder  and  valve.  Place  sufficient 
oil  in  the  basin  under  the  crank  so  it  will  stand  one  inch  above  the 
bottom  of  crank  discs.  When  receiving  a  new  engine  from  the 
shops  with  visible  stuffing-box  and  water  drain  ,  before  you  lill 
the  crank  case  with  oil,  previous  to  starting,  pour  water  in  opening 


Fig.  1. 

in  frame  into  pocket  under  piston  rod  stuffing-box,  until  water 
overflows  through  trap  connected  therewith  attached  to  outside  of 
frame.  Fill  cylinder  lubricator  and  start  it  to  feeding.  Fill  oil 


284  HANDBOOK    ON    ENGINEERING. 

pump,  and  pour  engine  oil  into  pocket  on  main  bearings.  Fill 
eccentric  oiler  -and  start  it  feeding.  After  the  steam  chest  and 
cylinder  are  warm,  turn  the  engine  over  by  hand  to  see  that  all  is 
free  and  right  to  start. 

Open  the  throttle  valve  gradually,  start  eny'iir  xlmvly.  After 
the  engine  is  up  to  speed,  pump  five  or  six  strokes  of  oil  into 
cylinder  with  oil  pump.  '  The  oil  should  flow  in  streams  through 
both  pipes  on  the  crank  cover  into  the  pockets  of  the  main  shaft 
bearings. 

This  oil  passes  from  the  main  bearings  through  the  crank  pin 
and  is  distributed  over  cross-head  pin  and  slides.  Occasionally 
clean  out  the  oil  passages  in  crank  pin. 

Supply,  as  needed,  a  little  fresh  oil  to  the  basin,  and  if  the 
oil  in  the  engine  bed  becomes  thick,  gritty  or  dirty,  so  as  not  to 
flow  freely  through  oil  passages,  draw  it  off  and  replace  with  fresh 
oil.  Filter  the  old  oil  and  use  it  over  continuously.  Use  a  pure 
mineral  oil  that  will  not  thicken  by  the  churning  it  receives. 

Serious  damage  and  cutting  of  the  cylinder  and  valve  will 
result  from  allowing  the  lubricator  to  cease  feeding,  even  for  a 
few  minutes.  If  your  engine  is  a  new  one  from  the  shops,  feed 
plenty  of  oil  through  the  lubricator  and  oil  pump  for  the  first 
few  weeks  after  starting.  Use  one  drop  of  oil  per  minute  for  each 
ten  horse-power,  or  ten  drops  per  minute  for  100  horse-power 
engine,  for  the  first  thirty  days  ;  after  which,  one-half  this  amount 
will  be  sufficient,  if  the  oil  is  of  good  quality.  If  your  boiler  is 
priming  or  foaming,  use  double  the  quantity  of  oil  to  protect  the 
cylinder  and  piston  from  cutting.  A  little  graphite  fed  into 
cylinder  is  very  beneficial. 

The  governor*  —  Fill  the  cups  on  governor  bearing  with  grease 
and  give  the  cap  J  turn  every  day.  Screw  the  cap  to  the  stuffing- 
box  on  dash  pot  loosely,  only  using  your  hand  to  turn  the  cap. 
The  governor  should  be  taken  apart  every  two  or  three  months 
and  bearings  cleaned  with  coal  oil  to  remove  gum.  If  governor 


HANDBOOK    ON    ENGINEERING.  285 

has  a  dash  pot,  it  should  be  refilled  with  glycerine  once  or  twice 
a  year.  Oil  may  be  used  in  the  dash  pot  in  place  of  glycerine, 
unless  the  engine  is  in  a  cold  room  where  the  oil  is  liable  to 
congeal.  To  refill  dash  pot,  unscrew  cover  on  end. 

In  taking1  the  governor  apart,  allow  the  sliding  block  which 
holds  the  end  of  the  governor  spring  to  remain  with  its  outer  edge 
on  a  line  with  a  mark  across  the  face  of  the  slide,  and  in  re- 
adjusting the  spring,  place  the  same  tension  on  it  as  before, 
which  can  be  ascertained  by  measuring  the  length  of  the  thread 
through  the  nuts  before  slacking  up  the  spring.  If  you  have 
trouble  with  springs  breaking  it  is  because  you  are  working 
them  under  too  much  tension.  The  speed  of  the  governor  is 
changed  by  moving  the  weight  on  the  lever. 

To  increase  the  speed  of  the  engine,  move  the  weight  on  the 
governor  lever  near  to  the  fulcrum  pin.  To  reduce  the  speed, 
move  the  weight  out  toward  the  end  of  the  lever.  Tightening  the 
spring  will  also  increase  the  speed,  but  will  cause  the  engine  to 
"  race,"  unless  at  the  same  time  the  block  which  holds  the  end  of 
the  spring,  is  moved  toward  the  center  of  the  wheel.  The  proper 
way  to  change  the  speed  is  by  moving  the  weight,  allowing  the 
spring  to  remain  in  its  marked  position. 

Moving  the  block,  which  holds  the  spring,  towards  the  rim  of 
the  wheel,  will  make  the  governor  more  sensitive  and  regulate 
more  closely ;  but  if  moved  too  far,  this  will  cause  the  governor 
to  "  race."  Moving  the  block  towards  the  hub  of  the  wheel  has 
a  tendency  to  stop  the  "  racing,"  but  if  moved  too  far  the  speed 
of  the  engine  will  be  reduced  with  the  increased  load.  If  any  of 
the  bearings  of  the  governor  bind,  or  require  oiling  or  cleaning, 
the  governor  will  "race."  These  bearings  should  be  kept  clean 
and  in  good  condition  and  the  stuffing-box  to  the  dash  pot  must 
not  be  screwed  up  tight,  as  that  will  cause  the  governor  to  "  race  " 
when  set  for  close  regulation. 

The    face  of    the  slide  is    marked  with  a  line  where  the  outer 


286  HANDBOOK    ON    ENGINEERING. 

edge  of  block  which  holds  the  spring  should  be.  Figures  stamped 
on  the  face  of  the  slide,  give  length  of  end  of  eye-bolt  extending 
through  nuts.  This  gives  the  right  tension  to  the  spring. 
Tightening  the*  spring  will  give  closer  regulation,  but  will  cause 
the  governor  to  "  race  "  if  the  spring  is  too  tight.  "  Racing  " 
caused  by  over-tension  of  spring,  can  be  stopped  by  moving  block 
nearer  to  center  of  wheel. 

To  set  valve.  —  Should  you  wish  to  ascertain  if  the  steam 
valve  is  properly  set,  proceed  as  follows :  Take  off  the  cover  or 
elbow  on  outer  end  of  steam  chest,  so  you  can  have  access  to  end 
of  valve.  Turn  the  engine  over  until  the  valve  has  traveled  as 
far  as  it  will  go  towards  end  of  steam  chest.  Then  measure  from 
the  end  of  steam  chest  to  the  end  of  the  valve,  and  this  distance 
should  be  represented  by  the  figures  in  inches  and  fractions 
on  end  of  steam  chest.  If  measurements  do  not  agree,  set  valve 
by  screwing  the  valve  stem  at  the  ball  joint. 

Square,  braided  flax  packing  is  the  best  kind  for  piston  rod  and 
valve  stem.  Don't  screw  the  glands  up  tight;  allow  them  to  leak 
a  little.  The  valve  stem  has  only  exhaust  steam  —  don't  pack  it 
tight.  Screw  it  up  by  hand  only.  Screwing  the  piston  rod  gland 
up  tight  may  cause  the  piston  to  thump  or  pound  the  cylinder, 
and  heat  and  cut  the  piston  rod. 

Safety  caps*  —  The  safety  caps  attached  to  drip  valve  under 
the  cylinder  are  intended  to  break,  in  order  to  save  damage  to  the 
engine  if  water  enters  cylinder.  They  will  protect  the  engine 
from  breaking  if  the  amount  of  water  is  not  too  large  to  pass 
through  the  valves  and  pipes.  If  they  break,  they  have  accom- 
plished their  purpose  and  new  ones  should  be  attached. 

Eccentric*  —  Take  up  lost  motion  by  reducing  the  brass  liners 
between  the  lugs  on  eccentric  strap,  and  unscrew  and  dis- 
connect the  ball  joint  on  the  eccentric  rod  to  see  that  the  eccen- 
tric strap  will  turn  freely  on  the  eccentric.  If  a  close  fit  it  will 
heat,  cut,  seize  and  break  the  eccentric  rod  or  valve  stem.  Allow 


HANDBOOK    ON    ENGINEERING.  287 

the  eccentric  strap  to  run  loose ;  no  harm  if  it  knocks  a  little. 
It  will  not  wear  out  of  round  on  account  of  running  loose ;  it  is 
dangerous  to  run  with  the  strap  snug. 

Ball  joint, — Take  up  lost  motion  in  the  ball  joint,  on  the  valve 
stem,  by  unscrewing  the  joint  at  eccentric  rod  and  turning  or 
liling  off  the  face  of  the  brass  part  attached  to  the  valve  stem, 
so  as  to  allow  the  male  part  to  screw  in  a  greater  distance. 

Connecting  rod*  —  Take  up  the  lost  motion  on  the  crank  pin 
bearing  by  removing  the  cap  and  taking  out  two  of  the  steel 
liners ;  take  one  from  each  side,  put  the  cap  back  and  set  the 
nuts  up  snug.  Disconnect  the  cross-head  end  of  the  rod  by  re- 
moving cross-head  pin,  and  try  lifting  the  rod  up  and  down  to 
see  that  it  does  not  pinch  the  crank  pin.  If  it  pinches  the  pin 
when  the  bolts  are  drawn  up  snug,  place  the  liners  back  or  substitute 
thinner  ones.  Always  screw  the  cap  back  solid  on  the  liners,  and 
keep  in  sufficient  liners  so  the  cap  will  not  pinch  the  pin  when  the 
bolts  are  screwed  down  snug.  NEVER  RUN  THE  ENGINE  WITHOUT 

HAVING      THE      CAP-    SCREWED      UP     SOLID    AGAINST    THE    ROD,    with 

liners  between  if  needed,  to  make  the  proper  fit.  If  you  remove 
some  .of  the  liners  be  sure  to  take  out  an  equal  amount  from  each 
side,  for  if  you  take  out  more  on  one  side  you  are  liable  to  throw 
the  cap  at  an  angle  in  tightening  up  the  bolts,  which,  in  time, 
will  cause  the  bolt  to  break  and  is  liable  to  wreck  the  engine. 

The  brass  in  the  cross-head  end  of  the  connecting  rod  is  set  up 
by  a  wedge.  This  wedge  is  drawn  down  by  the  steel  bolt  until 
the  brass  is  forced  solid  against  the  shoulders  in  the  end  of  the 
connecting  rod,  which  prevents  any  movement  of  the  brass. 
The  upper  bolt  is  used  to  lock  the  wedge  in  position  ;  also  in 
withdrawing  the  wedge  when  the  brass  is  to  be  removed. 

To  take  up  lost  motion  in  the  cross-head  end  of  the  connecting 
rod,  remove  the  brass  and  file  an  equal  amount,  even  and  square, 
from  each  edge  of  the  brass,  so  as  to  allow  the  brass  part  to  come 
up  to  the  pin.  When  filing  the  brass,  try  the  pin  in  the  rod 


288  HANDBOOK    ON    ENGINEERING. 

and  do  not  file  enough  to  allow  the  brass  to  pinch  the  .pin  when 
the  wedge  is  screwed  down  solid.  If,  by  mistake,  too  much  is 
filed  off,  put  in  a  sheet  of  copper  or  sheet  brass  liner,  so  the 
wedge  may  be  drawn  snug  without  pinching  the  pin. 

Cross-head.  —  For  adjusting  the  lower  cross-head  slide,  take 
out  the  cross-pin,  turn  cross-head  J  round  with  the  lower 
brass  slipper  opposite  opening  in  engine  frame ;  loosen  nuts  and 
insert  paper  or  thin  metal  strips  between  cross-head  and  slipper. 
The  top  slide  will  never  require  adjustment.  The  lower  slide 
should  run  five  years  before  requiring  lining  or  adjustment. 
Turn  the  cross-head  pin  |  way  around  every  three  months.  This 
will  prevent  it  wearing  out  of  round. 

Main  bearing's;  —  To  take  up  lost  motion  in  the  main  shaft 
bearings,  remove  the  cap  and  file,  scrape  or  plane  an  equal 
amount  from  each  of  the  babbitt  metal  liners  or  strips  which  are  in 
the  main  bearings  under  the  inside  edge  of  the  cap.  Remove  the 
metal  evenly,  so  the  liners  will  remain  of  equal  thickness  at  each 
end.  Do  not  remove  enough  from  the  liners  to  allow  the  cap  to 
pinch  the  shaft  when  the  nuts  are  screwed  down  snug.  If,  by 
mistake,  too  much  metal  is  removed,  put  in  paper  strips  on  .top  of 
the  liners  so  the  cap  can  be  screwed  down  solid  without  pinching 
the  shaft.  You  can  tell  when  the  cap  pinches  the  shaft  by  turn- 
ing the  engine  over  by  hand  ;  it  will  not  turn  freely  when  the  cap 
is  too  tight.  With  proper  care  the  main  bearings  will  run  two 
years  before  requiring  adjustment.  NONE  OF  THE  BEARINGS  OF 

THE      ENGINE    SHOULD     BE    SO     TIGHT    AS    TO    PREVENT    TURNING  THE 

ENGINE  FREELY  OVER  BY  HAND.  Always  test  the  engine  in  this 
manner  after  adjusting  bearings. 

If  a  bearing-  heats,  stop  the  engine  immediately,  take  out  shaft 
or  box,  clean  out  the  cuttings,  scrape  smooth,  clean  out  oil  pass- 
ages and  run  bearings  loose. 

Heating  or  cutting  will  never  occur  if  liners  are  put  in  so  caps 
cannot  be  set  up  to  pinch  the  bearings  and  they  receive  proper 


HANDBOOK    ON    ENGINEERING. 


289 


lubrication  with  oil  five  from  grit  or  dirt.  After  adjusting  any 
of  the  bearings,  run  the  engine  for  a  few  minutes  ;  then  stop  the 
engine  and  feel  the  bearings  which  have  been  adjusted  to  see  if 
they  are  running  cool.  This  precaution  may  obviate  having  to 
shut  down  your  engine  while  performing  regular  duty. 

Do  not  allow  your  engine  to  run  with  bearings  so  loose  as  to 
thump  or  pound,  as  this  will  cause  the  bearings  to  wear  out  of 
round.  If  the  shaft  or  wheels  run  out  of  true  or  wabble,  it  is 
because  the  main  bearings  are  loose  and  should  be  taken  up. 
The  engine  will  run  smooth  and  noiseless  if  bearings  are  properly 
adjusted. 

THE  STEAfl  CHEST. 

Fig.  2  shows  a  section  through  cylinder  and  valve.  The  steam 
chest  is  bored  out  and  fitted  with  a  pair  o'  cylinders  or  bushings, 


which  have  supporting  bars  across  the  ports,  to  prevent  any  pos- 
sibility of  the  valve  catching  upon  the  ports. 

The  valve  is  of  the  hollow  piston  type  —  a  hollow  tube  with  a 
piston  at  each  end.     The  live  steam  is  entirely  upon  the  outside 

19 


290 


HANDBOOK    ON    ENGINEERING. 


of  this  piston,  pressing  equally  on  each  end  ;  the  exhaust  steam  is 
entirely  on  the  inside  of  the  piston,  so  the  valve  is  perfectly  bal- 


Fig.  3  is  a  Tandem  Compound. 

auced  and  can  easily  be  moved  by  hand  when  under  full  boiler 
pressure. 

Fig*  4  is  a  cross-section  of  cylinder  and  valve  of  the  Tandem 
Compound  engine.  The  cylinders  of  the  Ideal  Compound  engine 
in  Fig.  4,  the  stuffing-box  between  the  two  cylinders,  is  dispensed 
with  entirely.  It  is  replaced  by  a  long  sleeve  of  anti-friction 
metal.  This  sleeve  is  light  and  free  to  adjust  itself  central  with 
the  rod.  Grooves  are  turned  on  the  inner  surface,  so  as  to  form 
a  water  packing. 

Both  valves  of  engine  are  controlled  by  the  same  governor  on 
the  same  stem,  moving  together  and  varying  in  stroke  as  the  load 
and  steam  pressure  vary.  This  gives  the  advantage  of  automatic 
cut-off  in  both  cylinders  and  dispenses  with  the  complication  of 
double  eccentrics,  rock  arms,  slides  and  stuffing-boxes. 

The  high-pressure  cylinder  has  a  piston  valve,  same  as  used  in 
all  ideal  engines.  For  the  low-pressure  valve  in  order  to  bring  it 


HANDBOOK    ON     ENGINEERING . 


291 


into  line  with  the  high-pressure  valve  and  keep  clearance  spaces 
at  minimum,  which  thus  gives  a  quick  and  wide  opening  at.  the 
beginning  of  the  stroke,  in  order  to  reduce  the  pressure  on 
exhaust  end  of  high-pressure  piston. 


Fig.  4. 

The  cover  of  this  valve  is  held  in  place  by  springs  and  will 
lift  and  prevent  excessive  pressure  in  the  cylinder  from  water  or 
other  causes. 


FOR  INDICATING  IDEAL  ENGINES. 

The  illustration  (page  292)  shows  the  reducing  motion  at- 
tached to  engine  ready  for  taking  indicator  cards. 

To  apply  the  Ideal  Indicator  Rig:  Screw  slotted  stud  in 
cross-head  pin,  first  removing  the  cap  screw.  Set  the  slot  per- 
pendicular to  line  of  motion  of  cross-head.  Set  cross-head 
exactly  in  center  of  its  travel.  Fasten  on  top  of  bed  where  oil 
funnel  is  placed,  first  removing  the  oil  funnel. 

Lever  should  be  adjusted  so  it  will  travel  in  slot  without  strik- 


292 


HANDBOOK    ON    ENGINEERING. 


ing  bottom,  or  passing  out  at  top.  Make  sure  that  lever  will 
travel  freely  in  slot  without  binding.  Select  a  hole  on  string 
carrier  that  will  give  the  necessary  motion  to  indicator  drum. 


Fig.  5. 

With  string  attached  from  indicator  through  hole,  so  adjust  this 
carrier  that  lines  drawn  on  polished  surface  shall  come  exactly 
parallel  with  string.  Make  all  adjustments  while  cross-head  is 
in  center  of  its  travel. 


POINTS     ON     STARTING     AND    RUNNING    A    WESTINGHOUSE 
COMPOUND  ENGINE. 

In  the  compound  engine,  the  automatic  governor  is  located 
on  the  shaft  inside  an  inclosed  case  tilled  with  oil,  whi^h  forms 
the  center  of  one  band  wheel.  Its  action  varies  the  travel  of 
the  valve  in  accordance  with  the  amount  of  work  demanded  of 
the  engine.  The  other  end  of  the  shaft  carries  an  ordinary 
band-wheel,  or  combination  pulley,  of  any  required  diameter  and 


HANDBOOK    ON    ENGINEERING. 


293 


face.  Set  up  the  engine  as  directed,  keeping  the  combination 
pulley,  or  band-wheel,  as  close  to  the  engine  as  possible.  Work 
the  wheel  on  by  turning  it  around  while  the  shaft  is  held  station- 
ary.  Do  not  attempt  to  drive  it  on. 


The  above  is  a  cut  of  the  Westinghouse  Compound  Engine. 

In  order  to  put  on  the  governor  case  with  its  band- wheel,  it  will 
be  necessary  to  first  remove  the  lid  or  cover  of  the  case,  so  as  to 
get  at  the  set  screws  and  key  way.  It  is  to  be  put  on  carefully 
and  should  not  be  driven  on  hard  enough  to  in  any  way  injure  the 
shaft.  The  keys  are  to  be  carefully  fitted  to  their  places,  and 
this  should  be  done  by  a  competent  mechanic.  It  is  not  pos- 
sible, in  every  case,  lor  the  wheels  to  be  put  on  the  engine  to 


294  HANDBOOK    ON    ENGINEERING . 

'.-•J: 

which  they  belong  and  keys  fitted  in  their  proper  places,  for 
various  reasons ;  therefore,  the  keys  are  left  as  they  come  from 
the  planer,  a  triile  full  of  the  required  size,  so  that  a  little  filing 
will  bring  them  to  a  good  fit.  If  the  keys  are  not  fitted  in  well 
and  carefully  at  the  start,  they  may  become  the  cause  of  a  great 
deal  of  subsequent  trouble ;  but  if  this  be  well  done  at  the 
beginning,  there  will  be  no  trouble  afterwards.  It  is  the  practice 
of  some  to  tie  a  tag  to  each  key,  designating  which  one  is  intended 
for  the  governor  case  wheel  and  for  the  band  wheel.  It  is  im- 
portant they  should  not  be  put  in  the  wrong  places.  If  the  band 
wheel  key  should  be  a  trifle  too  long,  no  harm  will  result ;  but  if 
the  governor  case  key  be  too  long,  it  will  protrude  through  the 
case  and  bind  the  eccentric  so  that  the  latter  will  not  have  free 
movement  across  the  shaft,  and  this  will  seriously  attract  the 
regulation  of  the  engine.  The  key  in  the  governor  case  should 
be  from  J"  to  J"  shorter  than  the  hub  in  the  governor  case,  to 
prevent  this  possibility.  When  the  keys  are  well  fitted  they  should 
be  driven  home  with  a  degree  of  tightness  depending  on  the  size  of 
the  engine,  and  the  set  screws  should  be  pulled  down  hard  and 
fast  to  hold  them.  The  keys  are  not  intended  to  lit  top  and 
bottom,  but  must  fit  exactly  sideways. 

After  the  governor  ^ase  with  its  wheel  is  properly  located  on 
the  shaft,  the  key  fitted  and  set  screws  pulled  down  hard  and  fast, 
the  governor  case  lid  is  to  be  put  on,  having  a  paper  gasket,  both 
on  its  outer  edge  and  at  the  hub,  to  prevent  leakage  of  oil  past 
these  surfaces  ;  and  it  is  to  be  bolted  up  tightly  in  its  place,  and 
the  governor  case  completely  fdled  with  cylinder  or  Dalzell  crank- 
case  oil,  through  a  connection  provided  for  this  purpose. 

Turn  the  engine  over  by  hand  to  make  sure  that  everything  is 
free.  Before  starting  the  engine  for  the  first  time,  oil  both  pistons 
thoroughly  by  taking  off  the  relief  valves  and  pouring  oil  into  the 
ports.  This  oil  will  work  through  the  valve  and  oil  it  also. 
Swing  aside  the  bonnets  from  the  crank  case,  and  see  that  the 


HANDBOOK    ON    ENGINEERING.  295 

latter  is  clean  and  free  from  the  cinders  and  dust  of  travel,  which 
o-enerallv  find  their  way  into  the  interior.  When  found  to  be  per- 

O  «/  »/ 

fectly  clean,  supply  oil  and  water  according  to  the  following 
directions :  Pour  in  water  until  it  makes  its  appearance  at  the 
outlet  of  the  overflow  cup  ;  then  pour  in  one  gallon  of  Westinghouse 
crank-case  oil  for  every  10  H.  P.  of  the  rating  of  the  engine  for 
the  smaller  compounds,  and  about  half  this  amount  for  the  larger 
ones.  This  will  raise  the  water  and  oil  in  the  interior  to  such  a 
level  as  to  almost  touch  the  crank-shaft,  so  that  the  connecting 
rods  will  be  plunged  into  the  liquid  at  every  revolution.  Takeoff 
the  eccentric  strap ,  clean  it  thoroughly,  also  clean  the  hollow 
eccentric  rod,  then  oil  and  replace  it.  Be  liberal  in  the  use  of  oil 
all  over  the  engine,  at  least  for  the  first  few  days.  Remember 
that  there  are  two  large  cylinders  and  a  valve  to  be  lubricated  and 
that  the  low-pressure  cylinder  gets  its  oil  only  through  the  high-pres- 
sure cylinder.  The  engine  should  now  be  ready  to  start.  Fill 
the  automatic  lubricator  on  the  steam  pipe  with  good  cylinder 
oil ;  fill  the  side  oil  cups  over  the  main  bearing  with  Westing- 
house  crank-case  oil,  and  open  the  drip-cocks  over  each  main 
bearing,  so  that  the  drip  is  continuous  and  regular  at  the  rate  of 
about  2  to  LO  drops  per  minute  from  each  cup,  according  to  the 
size  of  the  engine.  If  undue  service  is  required  of  the  engine,  so 
that  the  main  bearings  show  signs  of  heating,  the  amount  should 
be  increased.  Start  the  automatic  lubricator;  give  the  eccentric 
strap  some  direct  lubrication  from  a  squirt  can,  and  start  the  cup 
over  the  rocker  arm  to  feeding  from  each  cock. 

To  start  the  engine.  —  the  throttle  valve  being  closed,  open 
the  drain  cocks  in  the  throttle-valve  and  steam  and  exhaust  pipes, 
blow  them  out  thoroughly  and  then  close  them.  Open  both  cylin- 
der drain  cocks ;  raise  the  check  valve  on  the  crank  case  by  set- 
ting the  handle  down  ;  open  the  by-pass  valve.  Turn  the  engine 
rouod  until  the  high-pressure  piston  is  on  the  upper^center.  Now, 
open  the  throttle-valve  slightly,  for  the  purpose  of  warming  up  the 


296  HANDBOOK    ON    ENGINEERING, 

steam-chest  and  valve  equally,  as  otherwise  the  valve,  by  heating 
quickest,  may  expand  and  bind.  The  engine  being  on  its  center 
will  not  start.  When  sufficiently  warmed  up,  say  in  three  minutes 
by  your  watch,  close  the  throttle  value  for  an  instant  and  bar  the 
engine  off  the  center.  Then  open  the  throttle- valve  quickly,  but 
not  too  far,  which  will  insure  the  engine  passing  the  first  center. 
As  soon  as  the  engine  is  up  to  speed,  close  the  by-pass  valve 
tight  and  keep  it  closed  thereafter.  When  the  water  is  thor- 
oughly worked  out  of  both  cylinders,  close  the  cylinder  cocks 
and  keep  them  closed,  and  at  the  same  time,  close  the  check  valve 
and  open  main  throttle- valve  gradually  until  it 'is  wide  open. 
Never  attempt  to  regulate  the  speed  of  the  engine  by  the  throttle- 
valve. 

In  stopping  the  engine,  open  the  cylinder  cocks,  check  valves 
and  by-pass  valve  and  close  the  throttle  slowly,  so  as  to  allow  the 
engine  to  lose  speed  by  degrees.  Do  not  stop  suddenly,  as  the 
momentum  of  the  pistons  and  fly-wheels,  at  standard  speed,  is 
great,  and  the  strain  thrown  on  the  connecting  rods  and  crank- 
shaft, in  being  suddenly  stopped,  is  unnecessary  and  may,  in  time, 
become  injurious. 

In  general,  it  is  well  to  run  a  new  engine  empty  (that  is  with 
no  belts  on)  in  order  to  be  certain  that  everything  is  right ;  then, 
if  the  performance  is  all  right,  the  belts  can  be  thrown  on. 

With  a  compound  engine  properly  adapted  to  its  work,  not 
overloaded,  and  running  under  proper  conditions,  the  duty  of  the 
engineer  may  be  said  to  be  merely  nominal.  Nevertheless,  this 
engine,  when  it  requires  the  attention  of  an  engineer,  needs  the 
proper  kind  of  attention.  One  competent  man  can  operate  a 
very  large  number  of  these  engines.  What  is  meant  in  this  con- 
nection by  the  terms  ' '  properly  adapted  ' '  and  ' '  proper  condi- 
tions," is:  a  load  corresponding  to  a  mean  effective  pressure  in 
the  high-pressure  cylinder  not  exceeding  -one-half  of  the  boiler 
pressure  ;  a  boiler  pressure  as  high  as  possible,  the  engine  erected 


HANDBOOK    ON    ENGINEERING.  297 

in  compliance  with  the  directions  given,  and  the  directions  as  to 
lubrication  followed  carefully. 

The  wear  is  constant  in  one  direction,  namely,  downward. 
The  steam  acts  only  on  the  upper  side  of  the  pistons.  The  two 
crank-pins  are  exactly  opposite  each  other.  Each  piston  in  its 
downward  stroke  raises  the  other  piston.  The  direction  of  the 
wear  on  all  the  bearings  being  downward,  the  lost  motion  may  be 
considerable  without  detriment  to  the  quiet  running  of  the  engine. 
In  starting  and  stopping  the  engine,  however,  the  accumulated 
lost  motion  will  cause  a  noise,  inasmuch  as  this  motion  is  taken 
up  at  each  revolution ;  the  greater  the  amount  of  lost  motion,  the 
greater  this  noise  will  be  in  starting  and  stopping.  The  cause  of 
this  is  apparent ;  the  crank,  while  the  engine  is  stopping,  must 
pull  the  piston  down  and  the  effect  of  lost  motion  then  becomes 
similar  to  that  in  a  double-acting  engine.  The  effect  of  this 
action  is  not  conducive  to  good  wear  or  long  service.  It  allows 
a  shock  to  come  on  the  connecting  rod  strap  with  con- 
siderable force ;  this  wear,  therefore,  should  be  taken  up  fre- 
quently, but  it  can  be  allowed  to  accumulate  to  a  greater 
degree  than  will  be  possible  in  any  double-acting  engine. 
The  wear  is  taken  up  on  both  ends  of  the  connecting  rod  at  once, 
by  the  upper  bolt  at  the  lower  end.  The  engineer  on  opening 
the  crank  case  will  see  a  bolt  with  a  squared  end  and  a  lock  nut ; 
with  the  large  end  of  the  socket- wrench,  he  will  slack  off  the  lock 
nut,  and  then  with  the  small  end  of  the  wrench  he  will  turn  the 
bolt  to  the  left  until  the  brasses  come  up  solid ;  then  slack  off 
half  a  turn  and  set  up  the  lock  nut.  The  construction  of  the  rod 
and  the  way  in  which  a  single  wedge  is  made  to  take  up  both 
ends  of  the  rod  at  once,  is  evident  from  the  cut.  The  piston 
wrist-pins,  if  worn  or  cut,  should  never  be  dressed  off  or  turned 
down,  as  they  will  not  fit  the  bushing  or  have  a  proper  bearing. 
Order  a  new  pair,  and  throw  the  old  ones  away.  When  the 
babbitt  is  about  worn  out  of  the  main  bearing  shells,  they  can  be 


298  HANDBOOK    ON    ENGINEERING. 

re-babbitted  and  put  back  again.  The  cylinder  packing  rings 
will,  after  much  wear,  become  unfit  for  service,  and  will  allow 
steam  to  blow  past  the  pistons  into  the  crank-chamber.  There 
will  be  at  all  times,  when  the  engine  is  running  loaded,  a  small 
amount  of  vapor  arising  in  the  crank-case.  This  does  not 
necessarily  indicate  that  there  is  a  leakage  of  steam  past  the 
pistons,  as  the  heat  generated  by  the  splashing  of  the  water  on 
the  hot  pistons  and  cylinders,  and  by  the  leakage  of  the  hot 
water  of  condensation  past  the  pistons,  will  heat  up  the  water 
contained  in  the  crank-case,  until  it  vaporizes  slightly.  New 
packing  rings  can  be  easily  sprung  into  place  by  the  engineer. 

The  principal  duties  of  the  engineer  will  be  to  see  that  the 
automatic  lubricator,  which  oils  the  cylinders  and  valve  and  the  oil 
cup  over  the  rocker  arm,  perform  their  work  properly  and  regu- 
larly. Feed  slowly,  drop  by  drop,  according  to  the  requirements 
of  the  engine.  The  engineer  must  also  see  that  the  oil  tanks  on 
the  sides  of  the  engine  are  supplied  with  oil  and  fed  slowly,  drop 
by  drop,  into  each  main  bearing. 

The  inclosed  construction  of  the  engine,  whereby  all  oil  used 
in  lubrication  is  completely  distributed  on  the  wearing  surfaces 
and  is  prevented  from  wasting,  renders  it  unnecessary  for  the 
engineer  to  pay  as  close  attention  to  this  engine  as  to  any  other, 
as  it,  in  a  sense,  lubricates  itself.  The  crank-case  bonnets  should 
be  removed  regularly,  preferably  every  morning,  as  it  is  the  work 
of  Only  a  few  minutes.  The  interior  of  the  engine  should  be 
examined  to  make  sure  that  no  nuts  or  bolts  (of  which  there  are 
the  fewest  possible  number)  have  worked  loose,  bushings  worn 
out,  or  lost  motion  become  unduly  great ;  this  internal  examination 
is  absolutely  imperative,  at  least,  once  a  week.  The  proper 
drainage  of  water  in  the  steam  pipes  should  demand  his  attention, 
to  prevent  any  entrainment,  resulting  from  the  foaming  of  the 
boilers  or  from  any  other  cause.  Entrained  water  is  always  a 
prolific  source  of  trouble  in  steam  engineering ;  it  is  particularly 


HANDBOOK    ON    ENGINEERING.  299 

troublesome  in  all  piston  valve  engines,  even  with  Westinghouso 
engines,  which  are  provided  with  water  relief  valves.  The 
engineer  should  become  thoroughly  acquainted  with  his  engine  so 
as  to  understand  its  operation  and  principle,  and  be  at  all  times 
familiar  with  its  precise  condition.  All  adjustments  being  made 
in  the  shop  before  shipment,  it  is  unnecessary  for  the  engineer  to 
set  any  valves  or  take  any  part  in  the  adjustment  of  a  new  engine ; 
but  as  wear  occurs,  he  must  be  able  to  intelligently  make  the 
needful  adjustments  of  wearing  parts.  After  an  engine  has  run 
a  long  time,  the  downward  wearing  of  the  reciprocating  parts  will 
have  the  effect  of  throwing  the  valve  slightly  out  of  adjustment. 
That  is  to  say,  it  will  draw  the  valve  gear  downward  with  the 
shaft,  and  favor  one  cylinder  more  than  the  other.  The  valve, 
therefore,  will  require  resetting  occasionally,  but  not  at  all  fre- 
quently. It  should  be  adjusted  by  lengthening  the  eccentric  rod, 
just  the  amount  to  which  the  shaft  is  worn  downwards. 


MAIN    BEARING.  MAIN    BEARING. 

The  main  shaft  bearings  are  now  made  adjustable.  There  is 
a  slight  difference  of  construction  here  in  the  various  sizes, 
occasioned  by  limited  space  in  the  castings ;  but  they  are  all 
alike  in  this  respect,  that  the  bottom  half  of  the  main  bearing  is 
stationary,  being  turned  off  on  its  outer  shell  eccentric  with  the 
shaft  journal  and  held  down  firmly  by  a  long  set  screw  on  each 


300  HANDBOOK    ON    ENGINEERING. 

side,  which  prevents  it  from  rotating  or  from  rattling  loose.  The 
top  half  of  the  main  bearing  is  adjustable  downwards,  so  as  to 
follow  up  any  wear  either  of  the  babbitted  bearing  or  of  the  shaft. 
In  the  8  anctl3x8  and  (J  and  15x9  engines,  this  top  half  of 
main  bearing  is  adjusted  downwards  by  three  set  screws  located 
at  the  apexes  of  a  triangle,  and  the  bearing  is  locked  firmly  by 
three  tap  bolts  oppositely  placed  so  as  to  hold  it  secure  after 
adjustment,  In  the  case  of  all  larger  sizes  of  compound  en- 
gines, the  downward  adjustment  is  made  by  wedges  bearing  on 
the  inclined  tops  of  the  upper  half  of  the  bearing.  These  wedges 
are  moved  and  locked  by  a  tap  bolt  in  each  end,  which  passes 
through  and  draws  against  the  shell  of  the  crank-case  head.  The 
top  half  of  main  bearing  is  drawn  up  and  locked  in  position  after 
adjustment  by  tap  bolts  which  pass  down  through  the  top  shell 
and  are  screwed  into  the  bearing.  Some  of  these  bolts  and  wedge 
screws  are  inside  of  the  crank-case,  and  adjustment  must,  there- 
fore, be  made  while  the  engine  is  standing  idle.  It  is  customary 
to  mark  with  an  arrow  head  on  the  outside  of  the  crank-case  head 
to  indicate  which  way  the  wedge  will  move  to  tighten  up. 

The  proper  condition  of  the  compound  engine,  while  perform- 
ing its  work,  is  one  of  perfect  quiet,  without  leaks  of  steam  past 
any  joint  and  without  noise.  Any  noise  in  the  engine,  after  it 
has  attained  full  speed,  may  be  immediately  accepted  as  an  indi- 
cation that  something  is  wrong  and  the  engineer  should  familiar- 
ize himself  with  it,  so  as  to  be  able  to  discover  the  cause  and  the 
remedy.  Hot  bearings  may  be  said  to  be  unknown  in  this 
engine ;  occasionally,  however,  they  have  been  met  with  but  they 
are  always  traceable  to  the  use  of  improper  oil ;  dirt  and  grit  in 
the  oil ;  the  filling  up  of  oil  grooves,  or  the  wearing  out  of  the 
oil  grooves  in  the  main  bearing  shells ;  or  to  worn  out  or  broken 
packing  rings  in  the  piston.  The  eccentric  strap  is  the  only  point 
liable  to  run  dry,  and  the  engineer  should  see  that  the  oil  cup 
feeds  with  certainty.  All  joints  in  the  governor  are  bushed  and 


HANDBOOK    ON    ENGINEERING.  301 

these  bushings  are  provided  with  sufficient  oil  hples ;  they  can 
readily  be  replaced  with  new  ones  when  necessary.  In  replacing 
bushings,  always  be  careful  to  provide  ample  oil-holes,  the  same 
as  were  in  the  old  removed  bushings,  and  observe  the  same  pre- 
caution in  the  case  of  other  repairs. 

As  above  stated,  it  is  the  duty  of  an  engineer  to  know  in  what 
condition  every  part  of  his  engine  is  at  all  times.  All  wearing 
parts  should  be  examined  from  time  to  time,  so  they  can  be  re- 
placed before  they  are  entirely  worn  out, and  damage  is  done.  It 
is  too  late  to  find  out  that  a  bushing  needs  replacing  after  it  has 
been  worn  entirely  through  and  the  pin  has  cut  into  the  solid 
metal.  While  the  engine  is  built  of  the  very  best  materials  and 
with  the  greatest  care,  and  while  the  means  and  the  opportunity 
for  lubrication  are  the  best  known,  yet  it  is  not  claimed  that 
it  possesses  any  miraculous  virtues  by  which  it  will  run  on  for- 
ever without  any  attention  and  without  repairs.  Nowhere  is 
the  old  proverb  more  forcibly  demonstrated  than  in  the  case  of 
machinery,  that  "  A  stitch  in  time  saves  nine."  The  wearing 
parts  of  the  engine  are  few,  are  easily  reached  and  placed, 
and  the  engineer  who  waits  until  same  accident  happens  to 
announce  that  he  has  long  neglected  the  proper  inspection  of 
the  part  which  could,  at  the  proper  time,  have  been  replaced  at 
a  trifling  cost,  is  not  worthy  of  being  placed  in  charge  of  any 
machine  more  complicated  than  a  wheel-barrow.  The  same 
principle  will  apply  with  equal  force  to  machinery  of  every  type. 
There  is  a  proper  time  to  replace  worn  parts  and  a  time  it  is  too 
late  to  replace  them. 

HOW  TO  SET  THE  MAIN  VALVE. 

The  only  exact  and  final  setting  of  the  valve  is  by  means  of 
the  indicator.  As  the  valves  are  permanently  set  and  all  adjust- 
ments made  before  the  engine  is  shipped,  it  is  not  supposed  that 


302 


HANDBOOK    ON    ENGINEERING. 


the  engineer  will  have  occasion  to  reset  them.  Should  the  neces- 
sity for  setting  the  valves  arise,  however,  the  following  method 
will  be  sufficiently  accurate  :  Break  joints  and  take  off  the  throttle- 
valve.  The  steam  ports  in  the  bushing  will  then  be  seen  through 
the  steam  connection  S.  (This  opening  is  on  the  side  in  fact,  but 
is  here  shown  on  the  top  for  convenience.)  Bring  the  high- 
pressure  piston  exactly  to  the  top  of  its  stroke  by  turning  the 
shaft  in  the  direction  the  engine  runs.  This  may  be  ascertained 


B 


by  either  taking  off  the  water  relief  valve  and  measuring  through 
its  port,  or  more  conveniently,  by  bringing  the  middle  of  the  key- 
way  in  the  shaft  exactly  over  the  center  of  the  shaft.  The  key- 
ways  are  planed  exactly  with  the  cranks,  so  that  the  position  of 
the  key  way  is  the  position  of  the  high-pressure  piston.  With 
this  piston  at  the  top  of  its  stroke,  the  valve  edge  a  a,  should 
show  about  yL  of  an  inch  port  or  lead,  and  be  moving  towards 
the  right  as  you  stand  behind  the  engine.  If  out,  it  may  be 
brought  to  position  by  screwing  the  valve-stem  into  or  out  of  the 
valve  which  is  tapped  to  receive  it.  Be  sure  and  set  the  jam  nut 
solid  when  through. 


HANDBOOK    ON    ENGINEERING.  303 

After  a  test  of  n  compound  engine  has  been  completed  with 
the  indicator,  and  the  valve  has  in  this  manner  been  accurately 
adjusted,  marks  are  scored  on  the  end  of  the  rocker  arm,  at  its 
junction  with  its  supporting  bracket,  in  order  to  show  the  extreme 
points  of  oscillation  of  the  rocker  arm.  If,  therefore,  in  starting 
up  a  new  compound  engine,  the  eccentric  rod  is  too  long  or  too 
short,  these  marks  will  not  coincide  when  the  engine  is  turned 
round  by  hand,  to  examine  this  point.  The  eccentric  rod  must 
then  be  adjusted  with  the  nuts  provided  for  that  purpose,  until 
the  scored  lines  on  the  rocker  arm  will  coincide  exactly.  When 
this  rod  has  thus  been  proven  correct,  the  engine  should  then  be 
put  by  hand  on  the  dead  center,  with  the  high-pressure  piston  at 
the  top  of  its  stroke.  In  order  to  prove  this  upright  position  of 
the  high-pressure  piston  exactly,  two  lines  are  scored  on  the 
faced-off  end  of  the  crank-box  head  on  the  high-pressure  side,  to 
which  marks  the  keyway  in  the  main  shaft  must  be  brought 
exactly.  Then  remove  the  back  head  from  the  steam  chest  and 
measure  the  distance  from  the  rear  end  of  main  valve  to  the  end  of 
the  steam  chest,  while  the  engine  is  in  this  position.  This 
distance  measured  will  be  found  stamped  with  steel  figures  on 
the  finished  face  of  the  steam  chest,  underneath  the  back  head. 
If  the  valve  has  not  been  disturbed,  the  measurement  thus  taken 
will  agree  with  the  figures.  If  it  has  been  disturbed,  the  valve 
must  be  adjusted  to  correspond  with  the  measurement. 

ADJUSTHENT  OF  ECCENTRIC  STRAP  AND  CONNECTING  ROD. 

Before  starting"  the  engine  for  the  first  time,  the  eccentric  strap 
must  be  taken  off  and  both  the  strap  and  eccentric  carefully 
cleaned  and  lubricated  with  clean  oil.  The  eccentric  rod  is 
hollow  and  might  contain  dirt  or  other  injurious  matter,  and 
should  be  examined  and  thoroughly  cleaned  before  putting  on  the 
engine.  There  must  be  a  sufficient  number  of  liners  between  the 


304  HANDBOOK    ON    ENGINEERING. 

joints  of  the  strap,  so  that  when  the  bolt  is  pulled  up  hard  and 
tight  the  eccentric  strap  will  still  be  free  to  run  without  binding. 
After  the  bolt  has  been  tightened,  take  hold  of  the  strap  and 
shake  it  back  and  forth  to  be  sure  that  it  is  free.  If  it  binds  in 
the  least,  it  is  certain  to  heat  or  cut  either  itself  or  the  eccentric 
or  probably  both.  When  the  upper  ball  joint  on  eccentric  rod 
becomes  worn  it  should  be  adjusted  to  take  up  the  lost  motion 
promptly. 

As  to  the  connecting  rods,  the  lost  motion  should  be  simply 
taken  up  without  binding.  No  possible  good,  but  much  harm, 
can  come  from  too  tight  an  adjustment, 

GENERAL  INSTRUCTIONS    FOR  HOHE  REPAIRING. 

How  to  put  in  new  bushings  and  cut  the  oil  holes  and 
grooves*  —  When  new  bushings  are  shipped  to  fill  repair  orders, 
they  are  turned  to  gauge  so  as  to  fit  tightly  in  their  respective 
places.  A  very  careful  mechanic  may,  by  the  use  of  a  wooden 
block  and  hammer,  be  able  to  drive  in  bushings 'properly.  The 
much  safer  course,  however,  is  to  use  a  bolt  which  passes  through 
the  bushing,  and  a  nut  and  washer ;  by  screwing  up  the  nut  and 
taking  reasonable  care,  the  bushing  is  thus  drawn  surely  and 
gradually  into  place.  After  the  bushing  is  in  place,  the  oil 
grooves  must  then  be  cut  into  it  with  a  half-round  chisel  and 
hammer.  The  oil-holes  must  then  be  drilled  ;  these  latter  should 
be  large  and  free  ;  no  harm  can  come  from  having  them  too  large, 
but  much  trouble  will  result  if  they  are  too  small.  The  oil  should 
have  very  free  access  through  these  holes  to  the  grooves.  We 
have  conducted  a  long  series  of  experiments  to  determine  what 
form  or  style  of  oil  groove  would  produce  the  best  lubrication, 
and  consequently,  the  most  satisfactory  results  in  each  bushing, 
and,  therefore,  urge  that  grooves  be  cut  in  new  bushings  in  strict 
accordance  with  the  grooves  and  oil  holes  as  shown  in  the  old 


HANDBOOK    ON    ENGINEERING.  305 

bushing  which  has  been  removed.  This  course  is  safer  and  bet- 
ter than  to  try  experiments  of  your  own. 

How  to  rebabbitt  connecting  rods*  —  Connecting  rods  may  be 
re-babbitted  at  home,  if  preferred.  You  should  provide  yourself 
with  a  plug,  preferably  of  cast-iron,  turned  to  the  exact  diameter 
of  the  shaft  or  crank-pin  and  squared  accurately  on  the  end.  A 
perfectly  true  surf  are  is  then  required  on  which  to  lay  the  rod,  so 
that  the  plug  will  stand  in  its  proper  position,  exactly  square  with 
the  rod.  The  original  length  of -the  rod  must  be  known,  and  will 
be  furnished  by  us  on  application,  by  stating  the  number  of  your 
engine.  The  center  of  the  plug  must  then  be  placed  at  the  proper 
distance  from  the  center  of  the  eye  of  the  connecting-rod  pin,  and 
the  babbitt  metal  poured  into  place.  Moistened  lire-clay  will  be 
found  very  convenient  for  confining  the  molten  babbitt  metal 
within  its  proper  limits.  After  cooling,  the  babbitt  metal  should 
be  dressed  with  chisel  and  file.  Bear  in  mind  that  heavy  service 
is  required  of  these  connecting  rods,  and  that  the  engines  run  at 
higher  speeds  than  is  possible  in  any  other  type  of  engine,  hence, 
nothing  but  first-class  babbitt  metal,  or '"  genuine  "  babbitt 
metal,  as  it  is  called  in  the  trade,  will  answer  the  purpose.  I 
would,  however,  advise  that  the  brasses  be  sent  to  the  shop  to 
be  re-babbitt,  and  that  duplicates  be  kept  on  hand,  if  necessary. 

How  to  rebabbitt  main  bearing  shells*  —  This  is  a  very  diffi- 
cult piece  of  work  to  do  at  home,  and  it  is  not  recommended  that 
you  attempt  it ;  it  cannot  possibly  be  done  accurately  by  any  one 
without  special  appliances  for  the  purpose.  The  lines  of  the  bab- 
bitt, internally,  when  complete,  must  be  exactly  parallel  with  the 
outside  lines  of  the  shell,  else  the  shaft  cannot  lie  on  its  bearings 
with  equal  contact  throughout  the  length  of  the  shell.  The  lack 
of  equal  contact  will  cause  the  shaft  to  bind,  and  in  all  probabil- 
ity, the  limited  bearing  surface  will  cause  friction  and  heating. 
The  only  way  in  which  main  bearing  shells  can  be  properly  re- 
babbitted  at  home,  is  to  first  provide  yourself  with  what  is  called 

on 


306  HANDBOOK    ON    ENGINEERING. 

a  "jig,"  which  is  simply  a  special  device  that  holds  the  main 
bearing  shell  and  the  central  plug  in  their  relative  positions,  ex- 
actly, while  the  babbitt  metal  is  being  poured.  After  cooling, 
the  ends  of  the  shell  should  be  dressed  and  the  oil-holes  and 
grooves  must  be  properly  cut,  exactly  as  they  existed  when  the 
shell  was  new.  A  simple  and  more  satisfactory  method,  would 
be  for  each  owner  of  an  engine  to  purchase  an  extra  pair  of  main 
bearing  shells ;  in  this  way,  while  one  pair  of  shells  is  in  use  in 
the  engine,  the  other  pair  may  be  sent  in  for  rebabbitting,  with- 
out the  loss  of  time,  and  at  trifling  cost.  Use  nothing  but  iirst- 
class  "  genuine  "  babbitt  metal  in  the  main  bearing  shells. 

How  to  repair  worn  or  badly  scored  wrist-pins*  —  Instruc- 
tions on  this  point  are  very  simple:  Don't!  If,  on  examina- 
tion, you  find  you  have  allowed  the  wrist-pins  at  the  upper 
ends  of  the  connecting  rods  to  become  worn,  or  even  badly 
scored,  it  is  recommended  that,  having  bought  a  new  pair 
of  wrist-pins  and  rebabbitted  the  brasses,  you  immediately  take 
out  the  old  pins  and  throw  them  away.  It  is  useless  to  attempt . 
to  repair  worn  wrist-pins.  If  you  turn  them  down  until  they 
present  a  smooth  exterior  (as  some  have  proudly  announced  they 
have  done)  the  diameter  of  the  pin  is  so  reduced  that  it  will  not 
fit  the  brasses  and  the  reduced  bearing  surface  will  soon  destroy 
it.  Or,  if  you  attempt  to  use  a  badly  scored  wrist-pin  in  new 
brasses,  it  will  cut  them  out  so  rapidly  that  it  would  be  more 
economical  in  the  end  for  you  to  buy  new  wrist-pins  than  to 
attempt  to  use  the  old  ones.  The  service  on  the  wrist-pin  of  any 
engine  is  extremely  heavy.  These  pins  are  made  with  the  besi 
possible  care,  using  the  best  selected  materials,  and  after  machin- 
ing them  they  are  ground  in  special  machinery.  The  brasses  are 
lined  with  the  finest  possible  babbitt  metal  and  should  last  a  long 
time  under  heavy  duty  if  properly  lubricated  ;  yet,  the  use  of  an 
improper  oil  in  the  crank-case  —  either  volatile  or  gritty — nul- 
lities all  these  precautions.  Therefore,  if  you  lind  on  examina- 


HANDBOOK    ON    ENGINEERING. 


307 


tion,  that  the  wrist-pins  in  your  engine  have  become  badly  worn 
or  badly  scored,  I  would  urge  you  to  throw  them  away  and  buy 
new  ones. 


Where  the  inclosed  form  of  governor  is  used,  the  governor 
case  is  to  be  filled  completely  full  of  good  cylinder  oil,  or  with 
James  Dalzell  &  Son.,  Ltd.,  Crank-case  oil.  Use  nothing  else. 
A  nipple  is  screwed  into  the  face  of  the  inner  case  and  extends 
through  the  first  flange  of  the  wheel  in  a  radial  direction.  This 
nipple  is  closed  by  a  cap.  Turn  the  engine  around  till  this  nipple 
is  on  top  and  fill  the  case  entirely  full  through  the  opening.  The 
joint  at  the  outer  rim  of  the  case,  also  the  joint  on  face  of  hub,  is 
made  with  a  paper  gasket.  The  oil  is  prevented  from  escaping 
along  the  spindle  of  the  eccentric  and  out  past  the  eccentric  by  a 
leather  packing  ring  fitting  around  the  spindle  and  between  the 


308  HANDBOOK    ON    ENGINEERING. 

eccentric  and  the  face  of  the  case.  If,  after  service,  this  should 
leak  oil  when  the  engine  stands  still,  you  must  pack  it  tighter  by 
putting  in  a  thicker  packer-ring  of  leather,  so  it  shall  be  held 
tightly  in  its  place  and  prevent  the  passage  of  oil.  Be  careful  in 
locating  the  governor  case  on  the  shaft,  so  that  the  average  posi- 
tion of  the  eccentric  rod  shall  be  vertical  and  that  its  extreme 
positions  shall  be  alike  on  each  side  of  a  vertical  line  drawn 
through  the  center  of  eccentric.  Be  very  careful  as  to  the  lubrica- 
tion of  the  eccentric  strap  at  the  start.  After  it  runs  for  a  few 
weeks  and  gets  a  good  surface,  it  will  require  little  attention 
beyond  regular  oiling.  When  you  start  the  engine,  be  sure  to 
put  plenty  of  oil  on  the  eccentric  direct,  by  hand. 

The  best  means  for  lubricating  the  valve  and  pistons  is  an 
Automatic  Sight  Feed  Lubricator,  which  is  treated  of  elsewhere. 
It  is  manufactured  in  a  variety  of  forms,  many  of  which  are  very 
effective  in  their  working.  With  a  good  cylinder  oil,  the  number 
of  drops  per  minute  can  be  regulated  so  as  to  effect  the  greatest 
economy  of  oil  and  distribute  it  in  such  a  way  as  to  do  the 
engine  the  greatest  amount  of  good.  Any  other  system  of  lubri- 
cating the  cylinders  is  defective.  It  will  not  suffice  to  give  the 
engine  an  hour's  supply  of  oil  at  one  dose  and  then  allow  it  to  run 
without  any  cylinder  lubrication  for  the  remainder  of  that  hour. 
The  construction  of  the  Westinghouse  engine  is  such  as  to  be 
favorable  to  the  economy  of  oil  in  this  direction,  because  the 
pistons  moving  up  and  down  in  a  vertical  direction  do  not  have 
the  same  tendency  to  wear  as  in  the  case  of  a  horizontal  engine, 
where  the  heavy  piston-head  drags  back  and  forth.  These  im- 
mense bearing  surfaces,  moreover,  reduce  the  amount  of  pres- 
sure per  square  inch  to  a  minimum.  The  Automatic  Lubri- 
cator is  to  be  attached  to  the  steam-pipe,  within  easy  reach  of 
the  engineer,  so  that  it  can  be  refilled  without  loss  of  time. 
With  each  lubricator  is  packed  specific  directions  for  starting 
and  operating  it,  which  should  be  followed  carefully.  It  may 


HANDBOOK    ON    ENGINEERING.  309 

be  well  to  note  here  that,  in  order  to  get  the  best  results 
and  avoid  trouble,  no  other  than  a  first-class  cylinder  oil 
should  be  used  in  the  cylinders.  Approximately,  one  pint  of 
cylinder  oil  per  day  for  every  fifty  horse-power,  and  pro- 
portional, will  be  required  for  engines,  depending  on  the  amount 
of  work  to  be  done.  The  lubricator  furnished  on  each  engine 
will  serve  as  a  partial  index  of  the  quantity  of  oil  required. 
These  cups  are  not  intended  to  hold  over  8  to  10  hours'  supply 
in  any  case.  Feed  regularly  and  slowly.  The  use  of  Valvoline, 
or  600  W.  Vacuum  Cylinder  Oil,  made  by  the  Vacuum  Oil  Co., 
Rochester,  N.  Y.,  is  recommended,  although  there  are  others 
who  make  a  first-class  article. 

SOME  POINTS  ON  CYLINDER  LUBRICATION. 

44  In  the  first  place,  use  the  best  automatic  feed  cup  that  can 
be  secured.  Don't  be  satisfied  with  the  old-fashioned  direct 
feed,  or  a  cheap  automatic.  A  good  cup  will  save  many  a  hun- 
dred per  cent  on  its  cost  in  a  year.  Don't  get  the  kind  which,  on 
account  of  its  peculiarity  of  feed,  is  adapted  for  a  light  oil  only ; 
you  will  then  be  shut  out  from  using  a  dark  oil,  which  may 
be  far  more  serviceable  and  economical  in  every  respect.  Get 
a  cup  where  the  drop  of  oil  cuts  off  square  and  passes  either 
down  or  up  through  a  glass  tube  into  the  steam  pipe.  This 
kind  will  feed  oil  perfectly ;  if  yours  is  not  this  kind,  it  will 
pay  you  to  change  it." 

"Take  good  care  of  your  cup.  Don't  let  it  leak  around 
the  glass  tubes  or  other  joints,  for  if  it  does  the  water  will  escape 
as  it  condenses,  and  the  oil  will  clog  up  the  escape  pipe  and 
stop  feeding.  Use  in  it  only  the  best  grades  of  cylinder  oil, 
made  by  large  manufacturers  of  established  reputation.  Don't 
run  in  your  cylinders  any  kind  of  poor  stuff  that  may  be  offered, 
because  it  is  cheap ;  it  is  a  dangerous  experiment.  Feed  a  good 


310  HANDBOOK    ON    ENGINEERING. 

oil  sparingly  —  don't  drench  the  cylinder.  Too  much  oil  is  as 
bad  as  water  in  the  cylinder.  Engineers  have  been  known  to  run 
a  couple  of  quarts  per  day  of  cheap  oil  into  an  ordinary  sized 
cylinder,  and  thought  they  were  doing  just  right ;  this  is  positive 
abuse  of  an  engine.  In  almost  all  cases  where  too  much  oil  is  fed, — 
cut  it  down.  Two  to  four  drops  per  minute  on  engines  from  50 
to  150  H.  P.  are  all  that  is  necessary,  if  the  oil  is  good.  Just 
enough  to  do  the  work  and  no  more,  will  afford  best  results.  As 
long  as  the  valve  stem  does  not  cause  trouble,  you  may  know  the 
valves  are  working  smoothly  and  that  you  are  giving  oil  enough. 

AUTOMATIC  LUBRICATORS. 

An  Automatic  Sight  Feed  Lubricator  should  be  furnished 
with  every  engine,  which  enables  the  engineer  to  see  the  oil  as  it 
is  fed  drop  by  drop  to  the  engine.  The  construction  of  these 
lubricators  is  such  that  the  steam  entering  a  chamber  is  condensed 
and  this  water  of  condensation  finds  its  way  into  another  com- 
partment of  the  lubricator,  wherein  is  contained  the  oil  to  be  fed 
to  the  engine.  The  drop  of  water,  by  reason  of  its  greater  spe- 
cific gravity,  seeks  the 'bottom  of  this  oil  compartment  and  forces 
out  an  equivalent  bulk  of  oil  into  the  steam  pipe,  whence  it  is 
carried  by  the  current  of  steam  into  the  cylinders  and  is  distrib- 
uted upon  the  wearing  surfaces  intended  to  be  lubricated.  This 
method  insures  regularity  and  economy. 

There  are  numerous  automatic  lubricators  made  by  various 
manufacturers  throughout  the  country,  many  of  which  will  per- 
form their  functions  successfully.  I  have  used  several  of  the 
best  types,  and  consider  any  of  them  suitable  for  the  purpose ; 
jut  herewith  is  submitted,  with  description  of  the  cup  I  have 
been  using  for  some  years. 

This  is  the  up-feed  cup,  showing  an  external  view  and  sec- 
tional view  of  the  same.  Attachment  is  made  to  the  steam-pipes 


HANDBOOK    ON    ENGINEERING. 


311 


at  the  points  F  and  .A".  In  operation,  the  condensing  chamber  F 
provides  for  the  condensation  of  steam  which  enters  at  the  pipe  F. 
This  water  of  condensation  passes  down  through  the  valve  D  and 
through  the  tube  P  shown  in  the  section  and  discharges  into  the 
bottom  of  the  oil  vessel  A.  This  vessel  is  filled  with  oil  when  the 
cup  is  started,  the  height  of  oil  being  shown  in  the  index  glass  J. 


THE  ''DETROIT"  LUBRICATOR. 

The  operation  is  as  follows :  The  valve  N  being  opened,  the  valve 
D  is  opened  and  the  drop  of  water  is  allowed  to  pass  from  the 
condensing  chamber  F  downward  through  the  water  tube  and  into 
the  bottom  of  the  oil  chamber  A,  where  it  displaces  a  drop  of  oil 
of  equal  bulk  on  account  of  its  greater  gravity,  and  this  drop  of 
oil  is  forced  out  past  the  valve  E,  making  its  appearance  in  the 
feed  glass  H,  as  it  starts  on  its  way  to  the  steam-pipe.  It  is 
carried  by  the  current  of  steam  to  the  engine  and  lubricates  the 
valve  and  the  pistons.  When  the  oil  cup  is  empty,  the  valve  D 


312 


HANDBOOK    ON    ENGINEERING. 


is  closed  and  the  drain  valve  G  is  opened,  which  will  allow  tin- 
water  in  the  oil  chamber  to  be  blown  out  preparatory  to  the  re- 
filling at  the  plug  (7.  By  opening  the  valves  G  and  D,  steam  will 
be  blown  through  the  sight  glass  ,7,  thereby  clearing  the  same 
from  any  clogging  up  of  the  oil,  which  would  disfigure  it.  The 
amount  of  oil  to  be  fed  by  the  lubricator  will  be  regulated  by  the 
valve  Z>,  controlling  the  amount  of  water  admitted,  and  the  valve 
E  controlling  the  discharge  of  the  oil  into  the  sight  glass.  The 
valve  N  is  to  be  left  wide  open  in  operation  and  its  object  is  to 
provide  for  the  accidental  breaking  of  the  glass  //. 


Sketch  showing  proper  method  of  attaching  cup  to  prevent  the 

oil  from  dropping  into  the  well,  and  not  going  into 

the  cylinder. 

These  cups  should  be  attached  to  the  steam  pipe,  in  strict  ac- 
cordance with  the  instructions  contained  in  the  box  in  which  the 
lubricator  is  packed.  The  greatest  enemy  to  proper  performance 
is  leakiness ;  all  joints  must  be  absolutely  tight,  otherwise  the 


HANDBOOK    ON    ENGINEERING.  313 

water  of  condensation,  instead  of  performing  its  duty  of  displac- 
ing the  oil,  will  ooze  out  at  the  leaks  and  the  cup  will  refuse  to 
work.  In  most  cases,  provision  is  made  for  a  column  of  water 
which  may  stand  12"  or  more  in  height  and  enable  the  cup  to 
work  more  positively,  by  giving  it  a  greater  pressure  in  the  dis- 
placement chamber,  due  to  the  height  of  the  column.  A  suitable 
oil  is  essential  to  the  proper  working  of  such  a  lubricator,  as  well 
as  to  the  proper  lubricating  of  a  steam-engine.  An  improper  oil 
will  not  feed  through  the  cup  as  it  should,  on  account  of  its  dis- 
position to  disintegrate  and  go  off  in  bubbles,  when  exposed  to 
the  heat  of  the  steam. 

SETTING  A  PLAIN  SLIDE  VALVE  WITH  LINK  NOTION. 

The  setting  of  a  slide  valve  operated  by  a  link  motion  does 
not  differ  materially  in  principle  from  the  method  pursued  when 
setting  the  ordinary  slide  valve  driven  by  one  eccentric.  A  link 
motion  may  be  considered  as  a  means  of  driving  a  valve  by  two 
independent  eccentrics,  either  of  which  controls  the  functions  of 
the  valve  wholly  or  in  part,  according  to  the  position  of  the  link. 
Thus  when  the  link  is  in  either  extreme  position,  the  eccentric 
driving  that  end  of  the  link  in  line  with  the  link-block  pin  may  be 
considered  as  being  entirely  in  control  of  the  valve  action,  and, 
vice  versa,  when  the  link  occupies  the  other  extreme  position  of 
its  throw,  as  actuated  by  the  reverse  lever,  the  other  eccentric 
becomes  possessed  of  the  controlling"  function.  Practically, 
however,  the  operation  of  the  link  motion  is  very  complicated  and 
the  movement  of  one  eccentric  materially  modifies  the  action  of 
the  other.  Since  the  interfering  action  is  least  at  the  extreme 
positions  of  the  link  and  greatest  in  mid-gear,  the  plan  is  followed 
of  setting  the  valve  with  the  link  in  full  gear  both  forward  and 
backward  motion,  and,  as  before  stated,  the  procedure  is  on  the 
theory  of  independent  action  of  the  eccentrics. 


314 


HANDBOOK    ON    ENGINEERING. 


In  the  accompanying  diagram,  a  link  motion  is  shown  driving 
a  plain  slide  valve  without  the  intervention  of  a  rocker.  Each 
eccentric  is  set  with  reference  to  the  crank-pin,  the  same  as  it 
would  be  with  a  simple  slide-valve  engine.  The  eccentric  A  is 
set  on  the  shaft  with  the  same  angular  advance,  QMO,  as  would 
be  required  for  an  ordinary  engine  to  run  in  the  direction  indi- 
cated by  the  arrow.  Now,  since  the  crank  pin  is  at  (7,  if  it  were 
necessary  to  reverse  the  simple  engine  with  one  eccentric,  it  would 
be  necessary  to  change  the  position  of  the  eccentric  so  that  instead 
of  being  ahead  of  the  bottom  quarter  line  QM,  it  would  be  ahead 


of  the  top  quarter  line  PM  by  an  amount  of  angular  advance  made 
necessary  by  the  lap  and  lead  of  the  valve.  Therefore,  the  eccen- 
tric would  come  in  the  position  of  the  eccentric  A1,  or  with  its 
center  line  coinciding  with  MN,  giving  it  the  angular  advance 
PMN.  Now  it  should  be  clear  that  if  an  engine  is  to  be  equipped 
with  two  eccentrics,  so  that  it  may  run  with  equal  facility  in 
either  direction,  they  will  occupy  the  positions  A  and  A1.  We 
will  suppose  that  an  engine  having  a  link  motion  is  to  be  over- 
hauled and  the  valve"  motion  to  be  properly  set.  This  will  mean 
that  the  eccentrics  will  be  properly  located  for  the  correct  angular 
advance,  and  that  the  eccentric  rods  will  be  adjusted  to  the  right 
length.  When  these  conditions  are  obtained,  the  valve  should 


HANDBOOK    ON    ENGINEERING.  315 

perform  its    functions  properly  in    both    forward  and  backward 
motions,  and  also  when  the  link  is  "  hooked  up." 

Before  starting  to  set  the  valve,  it  is  best  to  take  a  general 
survey  of  the  valve  motion  parts  and  see  if  the  eccentrics  are 
somewhere  near  the  proper  location  on  the  shaft  relative  to  the 
crank-pin.  If  they  are  obviously  much  out  of  position,  they 
should  be  shifted  and  adjusted  as  near  the  correct  position  as 
possible  by  the  eye ;  doing  this  at  the  beginning  will  often  save 
confusion  and  much  time.  The  dead  centers  will  be  found  by  the 
method  given  on  page  195.  The  operation  should  be  carefully 
performed,  as  upon  it  depends  the  success  of  the  work.  After 
having  found  the  dead  centers  and  having  them  marked  so  that  no 
mistake  will  occur  when  "catching"  them  with  the  tram,  the 
valve  positions  may  be  taken  for  the  four  positions  ,  that  is,  front 
and  back  centers  in  forward  motion,  and  the  front  and  back 
centers  in  backward  motion.  Put  the  reverse  lever  in  full  gear  in 
one  motion  or  the  other,  whichever  is  most  convenient,  and  turn 
the  fly-wheel  in  the  direction  the  engine  would  run  for  the  given 
reverse  lever  position.  Suppose  the  link  stands  in  the  position 
shown  in  the  diagram,  the  fly-wheel  should  be  turned  in  the  direc- 
tion indicated  by  the  arrow  until  the  dead  center  is  reached, 
which  is  known  when  the  tram  drops  into  the  prick  mark.  The 
position  of  the  valve  is  then  noted  and  a  measurement  taken.  If 
the  valve  shows  the  steam  port  open,  measure  the  distance  with  a 
steel  scale,  or  it  may  be  done  by  sharpening  a  stick  wedge-shaped 
and  shoving  it  into  the  opening.  By  noting  the  depth  to  which 
it  goes  at  the  valve  face  the  opening  can  be  readily  measured  on 
the  removal  of  the  wedge.  We  will  suppose  the  distance  is  found 
to  be  ym  The  measurement  should  be  set  on  a  sheet  of  paper 
laid  out  as  follows  :  — 

FORWARD    MOTION.  BACKWARD    MOTION. 

Front  center,  Front  center, 

Back  center.  Back  center,  |"  lead. 


316  HANDBOOK    ON    ENGINEERING. 

It  will  be  seen  that  the  valve  opening  is  set  down  a«  being 
H"  lead,  and  as  being  on  the  back  center  in  the  backward  motion. 
After  having  verified  the  measurement  taken,  the  engine  can  be 
'"  turned  over  "  in  the  same  direction  as  before  until  the  opposite 
dead  center  is  caught  by  the  tram.  It  may  be  found  Hint  the 
valve  does  not  show  open  in  this  position  but  covers  the  steam 
port.  To  find  the  position  of  the  valve  edge  relative  to  the  steam 
port,  scribe  a  line  in  the  valve  seat  face  along  the  edge  of  the 
valve  and  then  turn  the  fly-wheel  until  the  valve  uncovers  the 
steam  port.  The  distance  the  valve  laps  over  when  the  crank  i« 
on  this  dead  center  can  then  be  readily  measured.  Suppose  the 
distance  is  found  to  be  J".  It  is  set  down  on  the  log  as 
follows :  — 

FORWARD    MOTION.  IJAOKWA  Rl>    MOTION. 

Front  center.  Front  center,  J"  blind. 

Back  center.  Back  center,  |"  lead. 

The  valve  position  is  put  down  as  being  J"  blind,  which  is  the 
same  as  saying  that  it  has  |"  negative  lead,  and  is  fully  as  com- 
prehensive as  the  latter  term.  The  reverse  lever  should  now  be 
thrown  into  the  opposite  gear  and  the  measurements  taken  for 
both  front  and  back  centers  the  same  as  has  been  described  for 
the  backward  motion.  It  may  now  be  supposed  that  when  all  the 
measurements  have  been  taken  the  log  reads  as  follows :  — 

FORWARD  MOTION.  BACKWARD  MOTION. 

Front  center,  ,J"  blind.  Front  center,  |"  blind. 

Back  center,  -f^"  lead.  Back  center,  |"  lead. 

When  in  forward  motion,  the  valve  is  open  T5¥"  on  the  back 
center  and  lacks  J"  of  being  open  when  the  crank  is  on  the  front 
center.  The  total  lead  due  to  the  angular  position  of  the 
eccentric  is  -f^"  minus  J"  —  TV'.  One-half  the  total  lead  should 
be  given  to  each  edge  of  the  valve  so  that  it  will  be  necessary  to 
lengthen  the  eccentric  rod  JB1,  -^"  -f-  *."  =  ^"  to  get  the  valve 


HANDBOOK    ON    ENGINEERING.  317 

into  its  proper  position.  A  little  reflection  will  show  the  reason 
for  lengthening  the  eccentric  rod  Bl.  In  speaking  of  the  front 
and  back  centers,  they  are  taken  to  coincide  with  the  crank  and 
head  ends  of  the  cylinder.  When  the  piston  is  at  the  crank  end 
of  the  cylinder,  the  crank  is  on  the  front  center.  By  referring  to 
the  log  it  will  be  seen  that  to  adjust  the  backward  eccentric  rod 
72,  it  will  also  be  necessary  to  lengthen  it.  The  valve  is  J"  blind 
on  the  front  center  and  has  |  "  lead  on  the  back  center.  The 
total  lead  is,  therefore,  f"  minus  J"—  J".  One-half  J"  =  J", 
which  being  added  to  the  amount  the  valve  is  lapped  on  the  front 
center,  makes  J",  or  the  amount  the  eccentric  rod  B  will  have  to 
be  lengthened  to  make  the  valve  open  equally  at  each  end  of  the 
piston  stroke.  The  opening  the  valve  has  when  the  crank  is  on 
the  centers  is  called  the  lead  and  in  the  ease  of  the  backward 
motion,  it  is  found  that  after  the  eccentric  rod  is  lengthened,  the 
lead  is  J",  which  is  too  much  for  most  cases  and  in  this  one  we 
can  assume  that  3^"  would  be  about  right. 

Before  explaining  the  adjustment  of  the  eccentric  for  the  cor- 
rect angular  advance,  it  will  be  in  order  to  call  attention  to  the 
necessity  of  making  the  adjustment  for  the  eccentric  rod  lengths 
first.  The  eccentric  rods  are  lengthened  or  shortened,  as  the 
case  may  require,  by  inserting  or  removing  liners  between  the 
eccentric  rods  and  straps  at  R.  Other  forms  of  construction 
provide  different  means  for  adjustment,  but  the  principle  is  the 
same  in  each.  It  will  be  noted  that  the  correct  length  for  the 
two  motions  is  obtained  by  adjusting  the  eccentric  rod  corre- 
sponding to  that  motion.  Any  attempt  to  correct  an  irregularity 
by  changing  the  length  of  the  valve  rod  F  will  result  erroneously, 
unless  both  eccentric  rods  require  the  same  amount  of  movement 
and  in  the  same  direction.  After  having  adjusted  the  eccentric 
rods  to  the  correct  lengths,  the  angular  advance  of  the  eccentric 
A  can  be  changed.  Place  the  crank  on  a  dead  center  and  have 
the  reverse  lever  thrown  in  the  backward  motion  and  then 


318  HANDBOOK    ON    ENGINEERING. 

loosen  the  set  screws  that  hold  the  eccentric  to  the  shaft  and  turn 
it  towards  the  crank  until  the  valve  shows  open  ^2",  and  then 
tighten  the  set  screws  on  the  shaft.  After  all  the  adjustments 
have  been  effected,  it  is  always  advisable  to  turn  the  engine  over 
again  and  catch  all  the  dead  centers,  so  that  the  correctness  of 
the  adjustments  can  be  verified.  After  taking  the  new  log,  it 
will  usually  be  found  that  some  slight  irregularities  have  been 
introduced,  especially  if  any  of  the  adjustments  have  been  consid- 
erable, as  the  changes  made  for  one  motion  will  affect  the  other 
slightly. 

The  link  motion  shown  in  the  cut  is  so  connected  that  the  lead 
increases  as  the  link  is  shifted  towards  the  center.  If  the  eccen- 
tric rods  be  oppositely  connected  to  the  link,  the  engine  will  run 
in  an  opposite  direction  for  a  given  reverse  lever  position  and  the 
lead  will  decrease  as  the  lever  is  shifted  towards  the  center.  The 
link  motion  for  hoisting  engines  is  quite  commonly  connected  in 
this  manner,  for  the  reason  that  the  engine  will  stop  when  the 
lever  is  put  on  the  center,  which  is  not  the  case  when  connected 
as  shown.  Of  course,  in  such  a  case,  the  admission  and  cut-off 
take  place  at  the  same  position  in  the  stroke  and  the  compression 
is  high,  but  with  a  light  load  the  engine  will  run  on  the  center, 
which  is  considered  objectionable  in  the  case  of  the  hoisting 
engine. 

VALVE-SETTING   FOR   ENGINEERS. 

Plain  slide-valve*  —  The  plain  slide-valve,  while  the  simplest 
valve  made,  is  perplexing  to  one  who  has  not  made  a  study 
of  it.  Unless  one  understands  the  principles  of  the  valve 
and  its  connections,  he  will  probably  meet  with  trouble  when  he 
attempts  to  set  it.  We  will  first  place  the  engine  (see  p.  195) 
on  the  dead  center,  and  will  simply  explain  the  other  steps 
that  have  to  be  taken.  In  the  first  place,  it  should  be  understood 
what  result  is  obtained  by  adjusting  the  position  of  the  eccentric 


HANDBOOK    OX    ENGINEERING.  319 

and  the  length  of  the  valve  stem.  The  position  of  the  eccentric, 
when  the  valve  is  set.  depends  upon  which  way  the  engine  is  to 
run  and  whether  the  valve  is  connected  directly  to  the  eccentric 
or  whether  it  receives  its  motion  through  a  rocker  which  reverses 
the  motion  of  the  eccentric.  When  the  valve  is  direct  connected, 
the  eccentric  will  be  ahead  of  the  crank  by  an  amount  equal  to  90°, 
plus  a  small  angle  called  the  angular  advance.  When  a  reversing 
rocker  is  used,  the  eccentric  will  be  diametrically  opposite  this 
position,  or  it  will  have  to  be  moved  around  180°  and  will  follow 
instead  of  lead  the  crank.  Shifting  the  eccentric  ahead  has  the 
effect  of  making  all  the  events  of  the  stroke  come  earlier,  and 
moving  it  backwards  has  the  effect  of  retarding  all  the  events. 
Lengthening  or  shortening  the  valve  stem  cannot  hasten  or  retard 
the  action  of  the  valve,  and  its  only  effect  is  to  make  the  lead,  or 
cut-off,  as  the  case  may  be,  greater  on  one  end  than  on  the  other. 
The  general  practice  is  to  set  a  slide-valve  so  that  it  will 
have  equal  lead.  The  lead  is  the  amount  that  the  valve 
is  open  when  the  engine  is  on  the  center.  To  set  the  valve, 
therefore,  put  the  engine  on  the  center,  remove  the  steam-chest 
cover  so  as  to  bring  the  valve  into  view,  and  adjust  the  eccentric 
to  about  the  right  position  to  make  the  engine  turn  in  the  direction 
desired.  Now  make  the  length  of  the  valve-spindle  such  that  the 
valve  will  have  the  requisite  amount  of  lead,  say  ^  of  an  inch, 
the  amojLint,  however,  depending  'upon  the  size  and  speed  of 
the  engine.  Turn  the  engine  over  to  the  other  center  and  measure 
the  lead  at  the  end.  If  the  lead  does  not  measure  the  same  as 
before,  correct  half  the  difference  by  changing  the  length  of  the 
valve-stem,  and  half  by  shifting  the  eccentric.  Suppose,  for 
example,  that  the  lead  proved  to  be  too  great  on  the  head  end  by 
half  an  inch.  Lengthening  the  valve-stem  by  half  of  this,  or  J 
inch,  would  still  leave  the  lead  J  inch  too  much  on  the  crank 
end.  That  is  to  say,  the  valve  would  then  open  too  soon  at  both 
head  and  crank  ends,  and  to  correct  this,  the  eccentric  would 


322 


HANDBOOK    ON    ENGINEERING. 


end,   towards   which  the  piston  is  moving,  has  just  commenced, 
and  the  exhaust  is  about  to  take  place  from  the  other  end. 

AT  POINT  OF  TAKING  STEAM. 

I 


Fig.  4. 

Fig*  4  shows  the  position  of  eccentric  and  valve  in  an  engine 
with  a  rocker-arrn. 

AT  POINT  Or  CUT- OF  FT 


Fig.  5. 

Fig.  5  shows  the  position  of  valve  and  eccentric  at  point  of 
cut-off. 

POS/T/ON  WHEN  COMPRESSION  BEGINS. 


Fig.  6. 

Fig1*  6  shows  point  01  compression. 


HANDBOOK    ON    ENGINEERING. 

I 


CHAPTEK     XIII. 

TAKING  CHARGE  OF  A  STEAfl  POWER  PLANT. 

It  is  frequently  the  case  that  an  cugineer,  en  assuming  charge 
of  a  steam  power  plant,  proceeds  as  though  lie  were  thoroughly 
familiar  with  the  condition  of  the  engine,  boiler  and  entire  sur- 
roundings. He  plunges  headlong  into  his  duties,  without  first 
taking  his  bearings.  A  skillful  physician  on  taking  a  case,  would 
not  proceed  in  this  manner  ;  neither  would  a  lawyer.  The  physi- 
cian would  feel  the  patient's  pulse,  look  at  his  tongue,  take  his 
temperature,  observe  his  color  and  ask  a  number  of  questions,  all 
for  the  purpose  of  enabling  him  to  make  a  correct  diagnosis  of 
the  patient's  ailment.  The  first  duty  of  ah  engineer,  when  he 
takes  charge  of  a  plant,  is  to  ascertain  the  arrangement  and  con- 
dition of  the  plant.  Since  the  boiler  is  the  most  important  mem- 
ber of  the  plant,  it  should  be  the  first  to  engross  his  attention,  and 
it,  together  with  its  connections,  should  be  examined  as  closely  as 
time  and  surrounding  conditions  will  permit.  He  should  look  the 
boiler  all  over,  internally  and  externally,  if  possible,  in  view  of 


324  HANDBOOK    ON    ENGINEERING 

mud,  scale,  grooving,  pitting  and  defective  braces.  The  furnace 
should  be  examined  next,  in  view  of  burnt-out  brickwork,  grate 
bars  and  door  linings.  It  may  be  that  the  furnace  has  distorted 
or  cramped  proportions,  or  it  may  be  too  large.  The  bridge  wall 
may  be  so  constructed  as  to  huddle  the  ilames  in  one  spot  on  the 
fire  sheets  of  the  boiler;  or  it  may  be  of  such  shape  and  in  such 
condition  as  to  cause  the  ignited  gases  to  become  dissipated  in 
the  combustion  chamber.  Even  the  combustion  chamber  itself 
may  require  the  service  of  a  bricklayer.  He  should  next  examine 
the  safety  valve  and  see  that  it  is  of  ample  capacity  to  relieve  the 
boiler  of  surplus  steam,  and  that  it  is  in  thorough  working  order. 
The  first  duty  of  an  engineer  when  entering  his  plant  at  any 
time,  is  to  ascertain  how  the  water  in  the  boiler  stands,  or, 
in  other  words,  just  how  much  water  the  boiler  contains.  He 
should  open  the  gauge  cocks  first  and  note  what  comes  from  each 
in  turn  ;  then  open  the  cocks  or  valves  connecting  the  glass  gauge 
and  note  the  water  line  there  shown.  He  should  also  blow  the 
water  column  out,  in  case  any  sediment  may  have  choked  any  of 
the  passages,  which  would  be  liable  to  give  a  false  impression  as 
to  the  actual  quantity  of  water  contained  in  the  boiler.  Should 
the  water  be  found  at  tho  correct  height,  he  may  now  proceed  to 
get  up  steam  ;  open  the  damper,  pull  down  the  banked  fire  and 
spread  it  evenly  over  the  grate,  adding  a  quantity  of  green  fuel. 
Allow  the  steam  to  rise  slowly ;  do  not  force  it.  This  applies 
especially  to  raising  steam  in  a  boiler  which  has  been  cold,  as  the 
expansion  of  the  parts  of  the  boiler  due  to  the  heat  should  take 
place  slowly  and  evenly;  otherwise,  the  life  of  the  boiler  will  be 
shortened.  While  waiting  for  the  steam  to  come  up  to  the  desired 
point,  the  engineer  should  now  get  his  engine  ready  for  the  day's 
run.  Fill  all  the  oil  cups  and  cylinder  lubricator,  so  as  to  be 
ready  to  operate  as  the  engine  starts.  With  a  hand  oil  squirt 
can,  go  around  all  the  small  brasses,  connections,  etc.,  and,  in  a 
word,  well  lubricate  all  the  parts  where  friction  takes  place.  If 


HANDBOOK    ON    P]NG1NKKKIN(}. 

you  have  an  oil  pump  for  your  cylinder  and  valves,  it  would  be 
well  to  inject  a  small  quantity  of  cylinder  oil  before  the  engine  is 
started,  while  the  stop-valve  is  open,  during  the  time  the  engine  is 
being  "  warmed  up."  After  the  engine  cylinder  is  warmed 
through,  the  fire  should  again  be  looked  at,  and  dealt  with 
according  to  the  indications.  Of  course,  the  water  gauge  glass 
must  be  looked  at  frequently,  not  only  while  raising  steam  in  the 
morning,  but  at  all  times  while  the  boiler  is  in  operation. 

Everything  being  in  readiness,  the  engine  is  started  slowly  at 
first,  the  speed  being  gradually  increased  until  the  limit  is  reached. 
The  day's  run  is  now  fairly  commenced.  A  boiler  should  be 
blown  down  one  gauge  every  morning  before  starting  the  day's 
run  to  get  rid  of  the  mud,  scale  or  anything  that  is  held  in 
mechanical  suspension  in  the  water.  Before  starting  in  the 
morning  and  at  noon  is  the  best  time  to  do  this,  as  the  sediment 
has  settled  to  the  bottom  during  the  night,  after  the  circulation 
of  the  water  has  stopped.  When  blowing  a  boiler  down,  always 
remember  to  open  the  blow- valve  slowly  —  be  careful  not  to  blow 
too  long,  and  then  to  close  the  valve  slowly. 

An  engineer  or  attendant  cannot  be  too  careful  in  handling 
the  many  appliances  with  which  a  steam  plant  is  equipped.  The 
principal  things  to  which  an  engineer  should  give  his  attention 
during  the  operation  of  his  boiler  day  by  day  are,  as  follows : 
The  maintenance  of  the  water  at  the  proper  level,  as  near  as  pos- 
sible, and  avoiding  fluctuations  in  the  pressure  of  steam.  See 
that  the  firing  is  done  correctly  and  economically  so  as  to  obtain 
from  every  pound  of  coal  all  that  is  possible  under  the  con- 
ditions existing.  The  raising  of  the  safety  valve  from  its  seat, 
at  least  once  daily ;  the  blowing  out  of  the  water  column  twice 
daily,  or  oftener,  if  the  water  used  is  very  dirty ;  the  frequent 
opening  of  the  water  gauge  cocks,  or  try  cocks,  as  they  are 
sometimes  called,  and  not  depending  entirely  on  the  gauge  glass 
for  the  correct  height  of  water ;  the  blowing  down  cf  t,he  boiler 


HANDBOOK    ON    ENGINEERING. 

one  gauge  every  day ;  the  keeping  of  all  valves,  cooks,  fittings, 
steam  and  water-tight,  clean  and  in  good  working  order. 

When  shutting  down  the  plant  for  the  night,  the  fires  should 
be  cleaned  out  and  the  live  coals  shoved  back  on  the  grates  and 
banked;  that  is,  green  coal  should  be  thrown  upon  them,  suffi- 
ciently thick  to  cover  all  the  glowing  fuel.  Pump  in  the  water 
until  it  reaches  the  top  of  the  glass  gauge.  This  should  be  done 
to  insure  a  sufficient  quantity  from  which  to  blow  down  in  the  morn- 
ing, and  also  to  allow  for  any  small  leaks.  Then  close  the  cocks  or 
valves  connecting  the  glass  gauge.  Should  this  glass  break  dur- 
ing the  night  and  the  valves  be  left  open,  there  would  not  be  much 
water  to  start  with  in  the  morning.  Leave  the  damper  open  a 
little,  just  sufficient  to  allow  the  gases  which  will  rise  from  the 
banked  fires  to  escape  up  the  chimney.  Finally,  make  sure  that 
all  the  valves  about  the  plant  which  should  be  closed,  are  closed  ; 
and  all  those  which  should  be  left  open,  are  open.  Of  course, 
the  foregoing  is  applicable  to  a  plant  where  there  is  no  night 
engineer.  But  in  any  case,  no  matter  how  many  assistants  an 
engineer  may  have  under  his  control,  he  should  be  familiar  with 
all  details  of  the  plant  under  his  charge. 

One  of  the  most  important  points  in  connection  with  the  opera- 
tion of  a  steam  boiler,  is  the  preventing  of  corrosion,  both 
internally  and  externally.  One  of  the  best  aids  to  secure  the 
well  working  and  longevity  of  the  steam  boiler,  or,  in  fact,  the 
whole  plant,  is  by  being  regular  and  punctual  in  a  certain  course 
of  treatment,  which  has  been  proven  toNbe  effectual  and  beneficial 
in  its  results.  All  conditions  do  not  require  the  same  methods  of 
treatment;  therefore,  it  is  absolutely  necessary  that  the  engineer 
in  charge  familiarize  himself  with  all  the  conditions  under  which 
his  plant  is  running,  for  then,  and  then  only,  can  he  intelligently 
prescribe  and  act  accordingly.  Above  all,  let  him  remember 
the  adage,  "  Eternal  vigilance  is  the  price  of  safety/*  especially 
where  a  steam  boiler  is  concerned. 


HANDBOOK    ON    ENGINEERING.  327 

ECONOMY   IN   STEAM   PLANTS. 

In  these  days  of  close  figuring  upon  expense  in  office  buildings 
and  manufacturing  plants,  what  may  at  first  appear  insignificant 
items  may  actually  make  all  the  difference  between  a  good  margin 
of  profit  and  an  actual  loss. 

The  fuel  expense  is  one  of  the  largest  in  the  operation  of  the 
majority  of  plants,  and  any  reduction  which  can  be  made  in  the 
amount  of  fuel  used,  while  maintaining  the  same  amount  of  power, 
is  considered  a  direct  gain.  The  evaporation  of  more  than  nine 
pounds  of  water  per  pound  of  coal,  is  looked  upon  with  suspicion 
by  many,  as  it  is  not  thought  possible  to  obtain  more  than  this 
amount  in  even  the  best  designed  and  well  regulated  furnaces  and 
boilers,  especially  when  the  firing  is  done  by  hand.  The  actual 
value  of  the  fuel  depends  upon  the  way  in  which  it  is  used,  fully 
as  much  as  on  any  other  factor.  The  heat  unit  in  the  coal  should 
be  as  much  as  possible  utilized,  as  in  one  pound  of  good  steam 
coal  there  is  about  14,000  B.  T.  U.,  and  about  10,000  of  this 
amount  can  be  utilized,  so  that  4,000  heat  units  are  lost.  The 
mixture  of  gases  in  a  furnace  depends  upon  the  amount  of  air 
used.  One  pound  of  coal  requires,  theoretically,  about  twelve 
pounds  of  air  to  burn  completely.  But,  in  practice,  about  twice 
this  amount  is  required  in  the  present  boiler  furnace.  To  have 
good  combustion  coal  requires  a  good  draft.  The  gases  are  con- 
sumed near  the  fire,  and  the  waste  gases  carry  the  heat  to  the 
boiler  on  their  way  to  the  stack.  The  boiler  ought  to  have  suffi- 
cient heating  surface,  or  the  hot  wasted  gases  ought  to  travel  a 
sufficient  distance  to  be  cooled  down  to  about  350  degrees  Fah- 
renheit ;  which  temperature  is  found  high  enough  to  produce  a 
good  draft  in  a  stack  of,  at  least,  100  feet  high. 

How  a  bad  draft  will  unnecessarily  increase  the  coal  bill,  is 
this:  That  of  all  the  fuel  burnt  to  perform  certain  work,  ascer- 
tained proportion  is  consumed  to  keep  the  heat  of  the  furnace  up 


328  HANDBOOK    ON    ENGINEERING. 

to  say,  212  degrees  Fahr.,  without  making  any  steam  whatever 
which  is  available  for  work.  This  quantity  varies  from  20  to  30 
per  cent,  according  to  conditions,  which  are  affected  by  various 
causes,  such  as  leakages  of  steam,  air,  or  water.  Now,  the  only 
available  power  for  work  which  we  get  from  our  fuel  is  the  margin 
between  this,  say  thirty  per  cent  required  for  the  said  purpose, 
and  what  we  generate  above  that.  An  engineer  should  notice  the 
general  condition  of  his  boiler  or  boilers,  and  the  equipments  of 
same ;  he  should  examine  the  boiler  both  inside  and  outside, 
ascertain  the  dimension  of  grates,  heating  surfaces,  and  all  im- 
portant parts.  The  area  of  heating  surfaces  is  to  be  computed 
from  the  outside  diameter  of  water-tubes,  and  the  inside  diameter 
of  fire-tubes.  All  the  surfaces  below  the  main  water  level  which 
have  water  on  one  side  and  products  of  combustion  on  the  other, 
are  to  be  considered  as  water-heating  surfaces.  If  he  finds  that 
the  boiler  does  not  come  up  to  what  he  thinks  it  should,  he  should 
put  the  boiler  and  all  its  appurtenances  in  first-class  condition. 
Clean  the  heating  surfaces  inside  and  outside  of  boiler,  remove 
all  scale  from  flues  and  inside  of  boiler ;  remove  all  soot 
from  inside  of  flues,  all  ashes  from  the  flame-bed  or  com- 
bustion chamber,  and  all  ashes  from  smoke  connections.  Close 
all  air  leaks  in  the  masonry  and  poorly  fitted  cleaning  door. 
See  that  the  damper  in  britching  or  smoking-flue  will  open  wide 
and  close  tight.  Test  for  air  leaks  through  the  crevices,  by 
passing  the  flame  of  a  candle  over  cracks  in  the  brick  work.  A 
good,  attentive  fireman,  who  understands  his  business  and  will 
keep  his  bars  properly  covered  without  choking  his  fires,  is  really 
worth  double  the  wages  of  an  ignorant  or  inattentive  one,  as  his 
coal  bills  would  certainly  prove.  All  an  engineer  can  do  is  to 
keep  the  steam  piston  and  valve  or  valves  tight.  Also  the  drains 
from  his  engine,  and  all  drains  on  steam  traps  in  the  plant  tight : 
also,  his  engine  cleaned  and  well-oiled,  and  not  keyed  up  too  tight. 
If  in  a  heating  plant,  he  should  see  that  the  back  pressure  valve  is 


HANDBOOK    ON    ENGINEERING. 


329 


at  all  times  tight,  as  it  does  not  take  much  of  a  leak  to  show  a 
difference  in  his  coal  bill  at  the  end  of  a  month.  He  should  keep 
all  valves  in  the  pumps  in  his  plant  tight,  and  see  that  the  pump 
piston  is  packed,  but  not  too  tight.  After  a  pump  is  packed,  you 
should  be  able  to  move  it  back  and  forth  by  hand ;  if  the  pump 
valves  leak  he  can  take  them  out  and  smooth  them  up  with  sand- 
paper. He  should  see  that  the  feed- water  to  the  boiler  is  at  least 
208  degrees  Fahrenheit ;  if  it  is  under  204  degrees,  his  heater  is  not 
right,  as  the  poorest  heater  will  heat  the  feed- water  to  204 ;  it 
would  be  well  to  overhaul  the  heater —  it  may  be  full  of  scale  ;  or, 
if  an  open  heater,  the  spray  may  be  off.  In  most  first-class 
plants,  the  feed-water  is  212  Fahrenheit. 

PRIMING. 

The  term  priming  is  understood  by  engineers  to  mean  the 
passage  of  water  from  the  boiler  to  the  steam  cylinder,  in  the 
shape  of  spray,  instead  of  vapor.  It  may  go  on  unseen,  but  it  is 
generally  made  manifest  by  the  white  appearance  of  the  steam  as 
it  issues  from  the  exhaust-pipe  as  moist  steam,  which  has  a  white 
appearance  and  descends  in  the  shape  of  "mist,  while  dry  steam 
has  a  bluish  color  and  floats  away  in  the  atmosphere.  Priming 
also  makes  itself  known  by  a  clicking  in  the  cylinder,  which  is 
caused  by  the  piston  striking  the  water  against  the  cylinder  head 
at  each  end  of  the  stroke:  Priming  is  generally  induced  by  a 
want  of  sufficient  steam-room  in  the  boiler,  the  water  being  car- 
ried too  high,  or  the  steam-pipe  being  too  small  for  the  cylinder, 
which  would  cause  the  steam  in  the  boiler  to  rush  out  so  rapidly 
that,  every  time  the  valve  opened,  it  would  induce  a  disturbance 
and  cause  the  water  to  rush  over  into  the  cylinder  with  the  steam. 


330 


HANDBOOK    ON    ENGINEERING. 


TABLE  OF  PROPERTIES  OF  SATURATED  STEAM. 


Pressure  in  h 
pounds  per 
square  Inch 
above  vacuum  II 

Temperature 
in  degrees 
Fahrenheit. 

Total  heat 
in  heat  units 
from  water 
at  32°. 

Heat  in  liquid 
from  32° 
in  units. 

Heat  of  vapor- 
ization or 
latent  heat  in 
heat  units. 

till 

111! 

Volume  of 
one  pound 
in  cubic  feet. 

Factor  of 
equivalent 
evaporation 
at  212°. 

Total  pressure 
above 
vacuum. 

1 

101.99 

1113.1 

70.0 

1043.0 

0  00299 

334.5 

.966 

1 

2 

126.27 

1120  5 

94  4 

1026.1 

0.00576 

173  6 

.9738 

2 

3 

141.62 

1125.1 

109.8 

1015.3 

0  00844 

118.5 

.9786 

3 

4 

153  09 

1)28.6 

121  4 

1007  2 

0  01107 

90  33 

.9822 

4 

5 

162.34 

1131  5 

130.7 

1000  8 

0  01366 

73  21 

.9852 

5 

6 

170.14 

1133.8 

138  6 

995.2 

0.01622 

61  65 

.9876 

6 

7 

176  90 

1135.9 

145.4 

990.5 

0  01874 

53.39 

.9897 

7 

8 

182  9-2 

1137  7 

151.5 

986  2 

0.02125 

47.06 

.9916 

8 

9 

188.33 

1139  4 

256  9 

982.5 

0.02374 

42  12 

.9934 

9 

10 

193.25 

1140  9 

161  9 

979  0 

0.02621 

38.15 

.9949 

10 

15 

213  03 

1146.9 

181  8 

965  1 

0.03826 

26.14 

1.0003 

15 

20 

227  95 

1151.5 

196  9 

964  6 

0.05023 

19  91 

1.005 

20 

25 

240.04 

1155.1 

209  1 

946.0 

0.06199 

16.13 

1  0099 

25 

30 

250  .  27 

115S.3 

219  4 

938.9 

0  07360 

13.59 

.0129 

30 

35 

259.19 

1161.  H 

228.4 

93  2.  b 

0  08508 

11.75 

.0157 

35 

40 

267  .  13 

1163  4 

236  4 

927.0 

0.09644 

10.37 

.0182 

40 

45 

274.29 

1165.6 

243  s6 

92-2.0 

0.1077 

9.285 

.0205 

45 

50 

280.85 

1167  6 

250.2 

9)7  4 

0  1188 

8.418 

.0225 

60 

55 

286  89 

1169  4 

256.3 

913  1 

0.1-299 

7  698 

.0245 

55 

60 

292.51 

1171.2 

261  9 

909  3 

0  1409 

7.097 

.0263 

60 

65 

297  77 

117-2.7 

267.2 

905.5 

0.1519 

6  583 

.0280 

65 

70 

302  71 

1174.3 

272.2 

902  1 

C.1628 

6  143 

.0296 

70 

75 

307  38 

1175.7 

276.9 

898  8 

0.1736 

5.760 

0309 

75 

80 

311  80 

1177.0 

281.4 

81)5  6 

0.1843 

5.436 

.0323 

80 

85 

316.02 

1178  3 

285.8 

892.5 

0.1951 

5  126 

0337 

85 

90 

320.04 

1179.6 

290  0 

889  6 

0.2058 

4.859 

.0350 

90 

95 

3-23.89 

]180  7 

294.0 

886  7 

0.2165 

4.619 

.0362 

95 

100 

3-27.58 

1181.9 

297  9 

884.0 

0.2271 

4.403 

.0374 

100 

105 

331  13 

1182.9 

301  6 

881  3 

0  2378 

4.206 

.0385 

105 

110 

334  56 

1184  0 

305  2 

878  8 

0  2484 

4  026 

0396 

110 

115 

337.86 

1185  0 

308.7 

876  3 

0.2589 

3  862 

.0406 

115 

120 

341.05 

1186.0 

312.0 

874.0 

0.2695 

3.711 

0416 

120 

125 

344  .  13 

1186  9 

315.2 

871.7 

0.2800 

3.571 

.0426 

125 

130 

347.12 

1187  8 

318.4 

869.4 

0.2904 

3  444 

.0435 

130 

140 

352.86 

1189.5 

324.4 

865  1 

0  3113 

3  212 

0453 

140 

150 

358.26 

1191.2 

330.0 

861  2 

0  3321 

3  Oil 

0470 

150 

160 

363.40 

1192.8 

335.4 

867.4 

0  3530 

2  833 

.0486 

160 

170 

368  29 

1194.3 

340.5 

853  8 

0.3737 

2.676 

.0602 

170 

180 

372.97 

1195  7 

345.4 

850.3 

0.3945 

2.635 

.0517 

180 

I'.K) 

377.44 

1197.1 

350.1 

847  0 

0.4153 

2.408 

0531 

190 

200 

381.73 

1198  4 

354.6 

843  8 

0.4359 

2.294 

0545 

200 

2-25 

391  79 

1201.4 

365.1 

836.3 

0.4876 

2.051 

0576 

225 

250 

400.99 

1204.2 

374.7 

829.5 

0.5393 

1.854 

0605 

250 

275 

409  ,50 

1-206.8 

383.6 

823  2 

0.5913 

1.691 

0632 

275 

300 

417.42 

1209.3 

391  9 

817  4 

0.644 

1  553 

0657 

300 

3-25 

424.82 

1211.5 

391)  6 

811  9 

0.696 

1  437 

0680 

325 

350 

431  90 

1213.7 

406.9 

806.8 

0.748 

1.337 

0703 

350 

375 

438  40 

1215.7 

414  2 

801  5 

0.800 

1.250 

0724 

376 

400 

445.15 

1217.7 

421.4 

796  3 

0.853 

1.172 

0745 

400 

5UO 

466.57 

1224.2 

444  3 

779.9 

1.065 

.939 

0812 

600 

HANDBOOK    ON   ENGINEERING.  331 

The  gauge  pressure  is  about  15  pounds  (14.7)  less  than  the 
total  pressure,  so  that  in  using  this  table,  15  must  be  added  to 
the  pressure  as  given  by  the  steam  gauge.  To  ascertain  the 
equivalent  evaporation  at  any  pressure,  multiply  the  given  evap- 
oration by  the  factor  of  its  pressure,  and  divide  the  product  by 
the  factor  of  the  desired  pressure.  Each  degree  of  difference  in 
temperature  of  feed-water  makes  a  difference  of  .00104  in  the 
amount  of  evaporation.  Hence,  to  ascertain  the  equivalent 
evaporation  from  any  other  temperature  of  feed  than  212°,  add  to 
the  factor  given  as  many  times  .00104  as  the  temperature  of 
feed-water  is  degrees  below  212°.  For  other  pressures  than  those 
given  in  the  table,  it  will  be  practically  correct  to  take  the  pro- 
portion of  the  difference  between  the  nearest  pressures  given  in 
the  table.  Example :  If  a  boiler  evaporates  3000  Ibs.  of  water 
per  hour  from  feed-water  at  200  degs.  Fah.  into  steam  at  100 
Ibs.  per  sqr.  in.  by  the  gauge,  what  is  the  equivalent  evaporation 
"  from  and  at"  ?  Ans.  3159.24  Ibs. 

Operation :  Temperature  of  feed-water  =  200  degs. 

Then,  212  —  200  =  12  =  difference  in  temperature. 

Then,  15  added  to  the  gauge  pressure  =  115. 

Looking  in  the  above  table  we  find  the  factor  1.0406. 

Then,  .00104  X  12=  .01248. 

And,  1.0406 
.01248 
1.05308 

Then,  3000  X  1.05308  =  3159.24  Ibs.  the  equivalent  evapo- 
ration. 

The  H.  P.  of  this  boiler  would  be  91.57. 


HANDBOOK    ON    ENGINEERING. 

HIGH  PRESSURE  STEAM. 

It  is  generally  believed  that  high-pressure  steam  is  cheaper  to 
use  and  costs  but  little  more  to  generate  than  low  pressure  steam. 
A  study  of  a  table  of  the  properties  of  saturated  steam,  to  be 
found  on  another  page  in  this  book,  will  show  why  high-pressure 
steam  is  economical  to  generate,  and  a  few  calculations  will 
prove  instructive  by  showing  what  may  be  excepted  from  its  use. 
To  generate  one  pound  of  steam  at  25  Ibs.  pressure,  absolute, 
requires  an  expenditure  of  1,155  thermal  units,  and  to  generate 
steam  at  200  Ibs.  pressure,  absolute,  requires  1,198  thermal  units, 
or  an  increase  of  only  43  thermal  units  for  an  increase  of  175  Ibs. 
pressure.  Further  investigation  shows  that  the  temperature  of 
steam  at  25  Ibs.  pressure  is  240°  and  at  200  Ibs.  pressure,  382°, 
the  difference,  142,  being  the  number  of  degrees  that  the  tem- 
perature of  steam  js  raised  with  an  expenditure  of  43  thermal 
units.  To  put  it  in  another  way,  the  temperature  of  the  steam 
has  been  raised  nearly  60  per  cent,  with  an  increase  of  less 
than  4  per  cent  in  the  number  of  thermal  units.  It  is  con- 
venient to  consider  that  the  generation  of  steam  takes  place 
by  two  different  steps,  one  of  which  is  raising  the  water  from 
32°  to  the  temperature  corresponding  to  the  pressure  of  the 
steam,  and  the  other  is  giving  off  the  steam  at  this  pressure, 
which  process  absorbs  a  quantity  of  heat  that  becomes  latent 
or  non-sensible.  At  25  Ibs.  pressure,  the  sensible  heat 
required  to  raise  one  Ib.  of  water  from  32°  to  240°  is 
209  units,  and  to  raise  it  from  32°  to  382  degrees,  the 
temperature  of  steam  at  200  Ibs.  pressure  requires  355  thermal 
units.  The  increase  in  the  sensible  heat  of  the  water,  there- 
fore, is  355  minus  209  =  146  units,  or  about  the  same  as  the  tem- 
perature increase  for  these  two  pressures,  which  is  142°.  It  is  thus 
clear  that  the  total  increase  in  the  number  of  heat  units  in  steam 
raised  from  25  Ibs.  to  200  Ibs.  pressure  is  small  (43°  as  found 


HANDBOOK    ON    ENGINEERING.  333 

above)  because  the  latent  heat  absorbed  in  the  formation  of  the 
steam  decreases  as  the  pressure  increases.  It  requires  less  heat 
to  generate  steam  from  water  raised  to  382°  at  200  Ibs.  pressure, 
than  from  water  previously  raised  to  240°  at  25  Ibs.  pressure. 
To  generate  higher  pressure  steam,  therefore,  we  must  first 
apply  enough  heat  to  bring  the  water  to  a  temperature 
corresponding  to  the  higher  pressure.  This  heat  will  be 
nearly  proportionate  to  the  increase  in  temperature.  Then 
enough  heat  must  be  applied  to  the  water  to  generate  the  steam, 
the  amount  of  heat  required  for  this  purpose  decreasing  as  the 
pressure  increases.  The  combined  result  of  these  two  processes 
is  that  it  takes  only  a  very  small  increase  in  the  total  heat  to  pro- 
duce the  higher  pressure  steam.  The  idea  may  be  suggested  that 
if  this  higher  pressure  is  obtained  at  the  cost  of  so  small  an  expen- 
diture of  heat,  it  would  not  be  reasonable  to  expect  a  large  gain 
in  economy  from  it,  since  it  is  not  possible  for  the  steam  to  do  a 
greater  amount  of  work  than  the  equivalent  of  the  heat  which  it 
contains.  This  would  be  true  were  it  not  for  the  fact  that  the 
larger  part  of  the  heat  in  the  steam  is  rejected  during  the  ex- 
haust. To  illustrate,  suppose  an  engine  to  exhaust  at  atmos- 
pheric pressure,  or  at  about  15  Ibs.,  absolute,  and  tha£  the  steam 
is  saturated.  As  may  be  determined  from  the  steam  tables,  there 
would  be  ejected  1,147  heat  units  per  pound  of  steam,  or  51 
heat  units  less  than  were  found  to  be  in  a  pound  of  steam  at 
200  Ibs.  pressure.  That  is  to  say,  under  the  above  assumption, 
there  are  available  only  51  heat  units  per  pound  of  steam  to  do 
the  work  in  the  engine  cylinder  when  the  steam  pressure  is  200 
Ibs.  But  we  also  found  that  the  increase  in  the  heat  units  in 
raising  the  steam  pressure  from  25  to  200  Ibs.  was  43,  and  hence 
the  increase  in  proportion  to  the  number  available  is  large, 
although  the  increase  in  proportion  to  the  total  number  required 


334  HANDBOOK    <>\    ENGINEERING. 

to  generate  the  steam  is  small.  This  shows  why  high-pressure 
steam  is  economical  to  generate  and  profitable  to  use.  It  should 
be  stated  that  the  only  way  in  which  the  full  benefit  can  be  de- 
rived from  high  pressure-steam  is  by  using  the  steam  expansively, 
keeping  the  terminal  pressure  at  release  as  low  as  possible.  I 
will  not  take  the  space  to  give  the  calculations  to  prove  this, 
but  will  compare  a  few  results  of  calculations.  Suppose  steam 
to  be  used  in  a  theoretically  perfect  engine  at  the  pressure 
of  25  Ibs.,  50  Ibs.,  100  Ibs.  and  200  Ibs.  We  will  assume  that 
in  each  case  the  cut-off  is  at  one-third  stroke,  giving  three 
expansions'and  a  terminal  pressure  of  one-third  the  initial  pres- 
sure. The  steam  consumptions  will  then  be,  respectively,  about 
161,  IG,  151,  and  14  Ibs.  per  horse-power,  showing  that  gain 
from  the  increase  in  pressure  is  very  slight.  On  the  other  hand, 
suppose  the  expansions  to  be  carried  to  the  atmospheric  pressure 
in  each  case.  The  consumptions  will  then  be  about  27,  15,  1] 
and  8  Ibs.  respectively",  showing  a  marked  decrease. 

Still  another  point  should  be  mentioned  in  relation  to  the 
relative  gain  that  is  to  be  expected  with  the  increase  in  pressure. 
Comparing  the  last  iigure,  it  will  be  observed  that  the  decrease 
in  consumption  when  the  pressure  increased  from  25  to  50  Ibs- 
was  27  minus  15  =  12  Ibs.,  or  44  per  cent.  Again,  when 
the  pressure  doubled  from  50  to  100  Ibs.,  the  consumption 
decreased  only  4  Ibs.,  or  27  per  cent;  and  when  the  pressure  was 
again  doubled  to  200  Ibs.,  the  consumption  only  decreased  3  Ibs., 
or  about  27  per  cent.  It  is  evident  from  this  that  the  saving 
from  an  increase  in  steam  pressure  grows  less  as  the  pressure 
increases,  and  this  is  found  to  be  the  case  in  actual  practice. 
There  is  another  reason  for  this,  also,  coming  from  the  losses 
incident  to  cylinder  condensation  and  re-evap*oration,  which  is 
1more  marked  where  there  is  a  wide  range  in  pressures  than  where 
the  pressures  are  more  uniform  throughout  the  stroke.  It  is  found 
that  where  the  steam  pressure  is  much  above  100  Ibs.  gauge  pres- 


HANDBOOK    ON    ENGINEERING.  335 

sure,  no  gain  will  result  from  a  further  increase  in  pressure  with- 
out compounding,  the  advantage  of  the  compound  engine  being 
that  the  extremes  of  temperature  in  the  cylinders  are  not  so  great 
as  with  a  simple  engine. 

USING   STEAfl   FULL   STROKE. 

The  steam  engine  is  nothing  in  the  world  but  an  enlargement 
upon  the  end  of  the  steam  pipe,  containing  a  piston  against 
which  the  steam  in  the  boiler  may  press.  The  piston  moves  a 
certain  distance,  and  then  the  steam  is  allowed  to  press  upon  its 
other  side,  while  the  steam  on  the  first  side  is  allowed  to  flow  into 
the  atmosphere  and  go  to  waste.  The  slide-valve  is  the  device  or- 
dinarily employed  to  admit  the  steam,  alternately,  to  opposite  sides 
of  the  piston,  and  to  permit  the  free  outflow  of  steam  from  the 
reverse  side  of  the  piston.  As  the  steam  presses  upon  the  piston 
the  piston  moves  forward  with  a  force  equal  to  the  pressure  of 
steam  per  square  inch,  multiplied  by  the  number  of  square  inches 
of  piston  surface.  Steam  occupies  the  entire  space  from  the  sur- 
face of  the  water  in  the  boiler,  to  the  piston  of  the  engine.  The 
steam  space,  therefore,  includes  the  steam  space  of  the  boiler,  the 
steam  pipe,  the  steam  chest,  and  the  cylinder  space  upon  one  side 
of  the  piston.  As  the  piston  moves,  the  entire  steam  space  be- 
comes a  little  larger,  by  reason  of  the  cylinder  space  becoming 
longer.  Thus  it  will  be  seen  that  all  of  the  steam  in  the  boiler 
and  pipe  and  engine,  would  expand  a  trifle  and  the  pressure 
become  somewhat  reduced,  were  it  not  for  the  fact  that  new 
steam  is  made  by  the  fire  as  fast  as  the  piston  moves  forward. 
By  this  means  the  steam  is  maintained  at  about  uniform  pressure. 
It  will  be  seen  that  the  pressure  is  produced  upon  the  piston 
by  the  generation  of  new  steam  from  the  water,  that  is,  the  fire 
causes  the  water  to  generate  a  quantity  of  steam,  and  this  quantity 
of  steam  forces  its  way  into  the  other  steam,  exerting  a  force 
upon  the  whole  body  of  steam  and  pushing  the  piston  ahead. 


HANDBOOK    ON    ENGINEERING. 

If  an  engine  piston  has  a  surface  of  100  square  inches  and 
a  stroke  of  ten  inches,  it  follows  that  the  piston  will  yield  a 
thousand  cubic  inches  additional  steam  space  by  its  movement 
during  one  stroke,  and  consequently,  the  fire  will  be  called  upon 
to  produce  1,000  cubic  inches  of  new  steam  for  each  single  stroke 
of  the  engine.  If  the  pressure  of  the  steam  be  eighty  pounds  to 
the  square  inch,  the  engine  piston  will  move  with  the  force  of 
8,000  pounds.  When  the  engine  has  completed  one  stroke,  we 
find  an  amount  of  power  exerted  equal  to  8,000  pounds  moved 
ten  inches,  and  we  then  open  the  exhaust  valve  and  empty  into 
the  atmosphere  1,000  cubic  inches  of  eighty-pound  steam.  We 
keep  on  doing  this  for  each  stroke.  Now  your  attention  is  par- 
ticularly called  to  the  fact  that  when  we  empty  the  steam  out  of 
the  cylinder,  it  is  just  as  good  as  when  it  went  into  the  cylinder; 
that  is,  it  was  1,000  cubic  inches  of  steam  at  a  pressure  of  eighty 
pounds  to  the  square  inch,  and  when  it  goes  into  the  atmosphere 
it  will  expand  into  over  6,000  cubic  inches,  at  fifteen  pounds 
pressure  to  the  square  inch,  or  the  same  pressure  as  the  atmos- 
phere. This  1,000  cubic  inches  of  steam  which  we  dumped  out 
of  the  cylinder,  is  precisely  the  same  quality  of  steam  as  the 
steam  which  we  have  penned  up  in  the  boiler;  and  which  we  have 
to  be  making  new  all  the  time  in  order  to  keep  the  engine  run- 
ning. Such  is  the  operation  of  the  steam  engine  which  receives 
its  steam  the  full  length  of  the  stroke ;  and  such  an  engine  may 
be  described  briefly,  as  a  very  wasteful  machine  which  throws 
away  steam  as  good  as  it  receives  it,  and  which  requires  the  gen- 
eration of  a  cylinder  full  of  full  pressure  steam  for  each  stroke. 
It  should  be  readily  understood  that  when  the  piston  has  com- 
pleted its  stroke,  and  just  before  the  exhaust  valve  is  opened  to 
allow  the  steam  to  escape,  the  cylinder  contains  1,000  cubic 
inches  of  steam  at  eighty  pounds  pressure,  which  it  is  capable  of 
expanding  into  many  thousand  cubic  inches  at  constantly  de- 
creasing pressure.  The  first  step  in  the  improvement  of  such  an 


HANDBOOK    ON    ENGINEERING.  337 

engine  would  be  to  so  arrange  things  as  to  get  some  benefit  from 
this  enormous  power  of  expansion.  The  full  stroke  engine  does 
not  get  one-half  of  the  power  before  it  throws  'the  steam  away. 
The  engine  which  we  would  have  referred  to  would  yield  a  power 
of  8,000  pounds  moved  ten  inches  at  each  single  stroke;  oo,000 
pounds  moved  one  foot  in  one  minute  is  a  horse-power ;  66,000 
pounds  moved  half  a  foot  would  be  the  same.  An  engine  using 
steam  full  stroke  is  such  an  extravagant  contrivance  that  wre,  now- 
adays, seldom  find  them  in  use.  There  are  certain  classes  of 
engines  built,  fitted  with  link  motions  for  driving  the  valve,  and 
they  are  arranged  so  as  to  carry  their  steam  full  stroke,  but  pro- 
vision is  also  made  for  quickly  hooking  up  the  link  and  suppress- 
ing the  full-stroke  feature. 

SLIDE  VALVE  ENGINES. 

If  we  have  an  engine  arranged  to  receive  its  steam  full  stroke 
and  to  dump  the  steam  out  into  the  air  in  as  good  condition  as  it 
was  received,  and  we  wish  to  get  some  of  the  benefits  of  the 
expansive  power  of  the  steam,  there  is  a  simple  way  of  doing  it 
and  without  any  great  change  in  the  engine,  and  that  is,  to 
lengthen  out  the  slide  valve  so  that  after  the  cylinder  is  half  full 
of  steam,  the  valve  will  shut  and  let  no  more  steam  enter.  Dur- 
ing the  balance  of  the  stroke,  the  entire  power  comes  from  the 
gradual  expansion  of  the  steam  shut  up  in  the  cylinder,  and  it 
will  be  readily  seen  that  whatever  power  we  succeed  in  getting  out 
of  the  expansion  of  the  steam,  is  pure  gain.  The  lower  the  pres- 
sure of  the  steam  is  when  it  is  exhausted  into  the  air,  the  more  it 
has  expanded,  the  more  power  we  have  gotten  out  of  it,  and  the 
more  we  have  gained.  It  may  be  said  in  a  few  words,  that  all 
slide-valve  engines  are  now  arranged  to  work  their  steam  expans- 
ively. But  it  is,  unfortunately,  found  that  the  slide-valve  pos- 
sesses a  peculiar  defect  which  prevents  the  system  being  carried 
very  far.  We  can  lengthen  out  a  slide-valve  so  as  to  cut  the 

'22 


338  HANDBOOK    ON    ENGINEERING. 

steam  off  at  any  desired  point  of  the  stroke,  and  we  must  then 
increase  the  throw  of  the  eccentric  in  order  to  properly  operate 
the  long  valve.  xBut  the  minute  we  do  this  we  lind  that  we  have 
interfered,  to  a  certain  extent,  with  the  proper  operation  of  the 
exhaust.  No  matter  what  we  do  about  the  admission  of  steam  or 
about  cutting  off  before  the  end  of  the  stroke,  we  must  arrange 
our  exhaust  to  take  place  at  a  certain  point  at  the  end  of  the 
stroke.  It  is  found  in  practical  operations  that  this  necessary 
quality  of  the  slide-valve  prevents  our  arranging  it  to  cut  off  the 
steam  properly  at  an  earlier  point  than  about  five-eighths  or  three- 
quarter  stroke.  The  consequence  is,  that  an  engine  with  two-feet 
stroke. will  receive  steam  18  inches,  then  have  (5  in.  of  expansion. 
It  may  be  fairly  said,  in  a  general  way,  that  about  all  the  slide- 
valve  engines  now  manufactured,  cut  off  the  steam  at  about  five- 
eighths  or  three-quarters  stroke  ;  and  it  may  be  further  said  that  this 
is  about  all  we  can  get put  of  a  slide-valve  engine.  Even  the  trifling 
expansion  got  from  such  engines  as  this,  represents  an  immense 
amount  of  money  in  the  course  of  a  year  in  large  establishments, 
but  it  is  not  good  enough  for  anyone  who  seeks  even  a  decent 
investment  of  money,  in  power-getting  appliances. 

REGULAR  EXPANSION  ENGINES. 

A  liberal  expansion  of  steam  being  desirable  and  the  slide- 
valve  proving  totally  incapable  of  providing  for  such  expansion, 
the  first  step  in  the  desired  direction  is  to  totally  discard  the 
slide-valve.  The  Corliss  valve  is  a  cylindrical  piece,  oscillating 
in  a  cylindrical  hole.  The  valve  does  not  fill  this  hole,  but  seats 
against  one  side  only.  Hence,  the  fitting  qualities  are  about  the 
same  as  with  the  slide-valve  and,  in  fact,  the  principle  is  about 
the  same,  the  Corliss  representing  a  portion  of  the  slide-valve, 
rolled  into  the  form  of  a  cylinder  and  operating  in  a  concave  seat. 
We  must  not  only  discard  the  slide-valve  arrangement,  but  in 
the  valve  arrangement  which  we  select,  we  must  secure  an  abso- 


HANDBOOK    ON    ENGINEERING.  339 

lute  independence  between  the  steam  admission  part  of  the  sys- 
tem and  the  exhaust  part.  The  slide-valve  is  one  chunk  of  cast 
iion,  letting  in  and  cutting  off  steam  at  its  outside  edges,  and 
opening  and  closing  the  exhaust  by  its  inside  edges.  When  one 
of  these  valve  edges  moves,  everything  else  has  to  move.  There 
is,  consequently,  no  independence  of  action.  In  the  Corliss 
engine  there  are  parts  to  let  steam  into  the  cylinder  and  to  quit 
letting  it  in  at  the  proper  time,  and  there  are  valves  to  let  it  out 
at  the  proper  time,  and  they  are  perfectly  independent  of  each 
other  in  all  of  their  movements.  The  consequence  of  this 
arrangement  is,  that  the  steam  valve  may  open,  steam  flow  into 
the  cylinder,  the  valve  suddenly  shut  and  chop  the  steam  off 
short,  the  piston  move  forward  in  its  stroke  by  the  expansion  of 
the  confined  steam,  and  finally,  be  let  out  by  the  opening  of  the 
exhaust  valve,  which  has  all  the  time  stood  ready  for  the  dis- 
charge. Here  we  have  a  regular  expansion  engine.  We  can  cut 
the  steam  off  as  early  in  the  stroke  as  we  desire,  and  hence,  have 
any  degree  of  expansion  we  desire.  And  we  can  do  this  without 
interfering  with  the  exhaust  valves.  It  is  found,  in  practice, 
that  an  engine  cutting  off  at  about  one-fifth  of  its  stroke  and 
expanding  the  other  four-fifths,  will  yield  the  fairest  practical 
economy. 

AUTOMATIC  CUT-OFF  ENGINES. 

In  order  that  those  not  posted  may  understand  what  is  meant  by 
the  term  "  Automatic  Cut-off  Engines,"  we  will  have  to  go  back  a 
step.  Take,  for  instance,  a  full-stroke  engine.  It  ought  to  be 
well  understood  how  the  ordinary  governor  does  its  work.  Sup- 
pose, for  instance,  that  there  is  no  governor,  and  that  we  regulate 
the  speed  of  the  engine  by  having  a  man  stand  at  the  throttle-valve 
all  the  time.  If  the  engine  runs  too  fast,  he  shuts  the  throttle- 
valve  a  little.  This  makes  the  steam  pipe  so  small  that  the  steam 
eannot  flow  fast  enough  to  keep  the  pressure  up,  and  consequently, 


338  HANDBOOK    ON    ENGINEERING. 

steam  off  at  any  desired  point  of  the  stroke,  and  we  must  then 
increase  the  throw  of  the  eccentric  in  order  to  properly  operate 
the  long  valve.  "But  the  minute  we  do  this  we  find  that  we  have 
interfered,  to  a  certain  extent,  with  the  proper  operation  of  the 
exhaust.  No  matter  what  we  do  about  the  admission  of  steam  or 
about  cutting  off  before  the  end  of  the  stroke,  we  must  arrange 
our  exhaust  to  take  place  at  a  certain  point  at  the  end  of  the 
stroke.  It  is  found  in  practical  operations  that  this  necessary 
quality  of  the  slide-valve  prevents  our  arranging  it  to  cut  off  the 
steam  properly  at  an  earlier  point  than  about  five-eighths  or  three- 
quarter  stroke.  The  consequence  is,  that  an  engine  with  two-feet 
stroke. will  receive  steam  18  inches,  then  have  6  in.  of  expansion. 
It  may  be  fairly  said,  in  a  general  way,  that  about  all  the  slide- 
valve  engines  now  manufactured,  cut  off  the  steam  at  about  live- 
eighths  or  three-quarters  stroke  ;  and  it  may  be  further  said  that  this 
is  about  all  we  can  get  put  of  a  slide-valve  engine.  Even  the  trifling 
expansion  got  from  such  engines  as  this,  represents  an  immense 
amount  of  money  in  the  course  of  a  year  in  large  establishments, 
but  it  is  not  good  enough  for  anyone  who  seeks  even  a  decent 
investment  of  money,  in  power-getting  appliances. 

REGULAR  EXPANSION  ENGINES. 

A  liberal  expansion  of  steam  being  desirable  and  the  slide- 
valve  proving  totally  incapable  of  providing  for  such  expansion, 
the  first  step  in  the  desired  direction  is  to  totally  discard  the 
slide-valve.  The  Corliss  valve  is  a  cylindrical  piece,  oscillating 
in  a  cylindrical  hole.  The  valve  does  not  fill  this  hole,  but  seats 
against  one  side  only.  Hence,  the  fitting  qualities  are  about  the 
same  as  with  the  slide-valve  and,  in  fact,  the  principle  is  about 
the  same,  the  Corliss  representing  a  portion  of  the  slide-valve, 
rolled  into  the  form  of  a  cylinder  and  operating  in  a  concave  seat. 
We  must  not  only  discard  the  slide-valve  arrangement,  but  in 
the  valve  arrangement  which  we  select,  we  must  secure  an  abso- 


HANDBOOK    ON    ENGINEERING.  339 

lute  independence  between  the  steam  admission  part  of  the  sys- 
tem and  the  exhaust  part.  The  slide-valve  is  one  chunk  of  cast 
iron,  letting  in  and  cutting  off  steam  at  its  outside  edges,  and 
opening  and  closing  the  exhaust  by  its  inside  edges.  When  one 
of  these  valve  edges  moves,  everything  else  has  to  move.  There 
is,  consequently,  no  independence  of  action.  In  the  Corliss 
engine  there  are  parts  to  let  steam  into  the  cylinder  and  to  quit 
letting  it  in  at  the  proper  time,  and  there  are  valves  to  let  it  out 
at  the  proper  time,  and  they  are  perfectly  independent  of  each 
other  in  all  of  their  movements.  The  consequence  of  this 
arrangement  is,  that  the  steam  valve  may  open,  steam  flow  into 
the  cylinder,  the  valve  suddenly  shut  and  chop  the  steam  off 
short,  the  piston  move  forward  in  its  stroke  by  the  expansion  of 
the  confined  steam,  and  finally,  be  let  out  by  the  opening  of  the 
exhaust  valve,  which  has  all  the  time  stood  ready  for  the  dis- 
charge. Here  we  have  a  regular  expansion  engine.  We  can  cut 
the  steam  off  as  early  in  the  stroke  as  we  desire,  and  hence,  have 
any  degree  of  expansion  we  desire.  And  we  can  do  this  without 
interfering  with  the  exhaust  valves.  It  is  found,  in  practice, 
that  an  engine  cutting  off  at  about  one-fifth  of  its  stroke  and 
expanding  the  other  four-fifths,  will  yield  the  fairest  practical 
economy. 

AUTOMATIC  CUT-OFF  ENGINES. 

In  order  that  those  not  posted  may  understand  what  is  meant  by 
the  term  "  Automatic  Cut-off  Engines,"  we  will  have  to  go  back  a 
step.  Take,  for  instance,  a  full-stroke  engine.  It  ought  to  be 
well  understood  how  the  ordinary  governor  does  its  work.  Sup- 
pose, for  instance,  that  there  is  no  governor,  and  that  we  regulate 
the  speed  of  the  engine  by  having  a  man  stand  at  the  throttle-valve 
all  the  time.  If  the  engine  runs  too  fast,  he  shuts  the  throttle- 
valve  a  little.  This  makes  the  steam  pipe  so  small  that  the  steam 
eannot  flow  fast  enough  to  keep  the  pressure  up,  and  consequently, 


340  HANDBOOK    ON    ENGINEERING. 

the  speed  goes  down.  If  the  engine  runs  too  slow,  he  opens  the 
throttle- valve  and  lets  the  steam  flow  free,  so  as  to  maintain 
higher  pressure.  Thus  it  will  be  seen  that  the  man  at  the  throttle 
regulates  the  engine  by  altering  the  pressure  with  which  the  steam 
acts  upon  the  engine.  An  ordinary  engine  governor  is  simply  a 
man  at  the  throttle.  When  the  engine  runs  too  fast  the  balls  fly 
out,  the  governor  valve  shuts  a  little  and  the  pressure  of  steam 
entering  the  engine  is  reduced,  and  so  on  through  all  the 
changes  continually  taking  place.  All  steam  engines,  in  which 
the  regulation  of  steam  is  effected  by  means  of  a  governor  operat- 
ing upon  a  throttle,  are  called  throttling  engines.  They  operate 
by  reducing  the  pressure  of  the  steam  admitted  to  the  engine,  and 
thereby  taking  so  much  of  the  vitality  out  of  the  steam.  It  is 
entirely  the  wrong  way  to  do  it.  After  once  spending  our 
money  to  get  up  pressure  in  the  boiler,  we  should  make  the 
greatest  possible  use  of  that  pressure,  so  long  as  we  are  taking 
the  steam  from  the'  boiler.  It  is,  therefore,  desirable  that 
the  full  boiler  pressure  should  be  admitted  to  our  cylinder ; 
and  the  question  arises  as  to  how  we  shall  be  able  to  regulate 
the  speed  if  we  do  not  tinker  with  this  pressure.  The  Automatic 
Engine  regulates  the  speed  by  the  simple  act  of  altering  the  point 
of  cut-off.  If  the  engine  is  cutting  off  at  one-fifth  stroke,  we  get 
a  power  equal  to  the  incoming  force  of  steam  for  one-fifth  of  the 
stroke,  and  the  expansion  of  the  steam  for  the  other  four-fifths  of 
the  stroke.  If  the  engine  runs  too  slow  we  cut  the  steam  off  a 
little  later  and  thereby  increase  the  average  pressure  during  the 
expansion.  The  Automatic  Engine,  then,  is  an  engine  which  cuts 
off  the  steam  at  an  earlier  point  in  the  stroke,  if  the  engine  runs 
too  fast,  and  cuts  it  off  at  a  later  point  if  it  runs  too  slow.  It  is 
the  duty  of  the  governor  to  say  just  when  the  steam  valve  should 
close  and  not  let  any  more  steam  into  the  cylinder.  In  the  Cor- 
liss Engine  the  steam  valves  open  wide  at  the  beginning  of  the 
stroke  and  let  full  boiler  pressure  smack  in  against  the  piston. 


HANDBOOK    ON    ENGINEERING. 

After  the  piston  has  advanced  to,  say  one-fifth  of  its  stroke,  the 
valve  shuts  up  as  quick  as  a  flash  and  the  expansion  begins.  If 
the  engine  starts  too  slow,  the  governor  will  hold  the  steam  valve 
open  a  trifle  longer,  but  will  not  interfere  with  its  full  opening  at 
the  beginning  of  the  stroke,  or  with  its  flash-like  closing  when 
the  cut-off  is  to  take  place.  During  all  these  operations  of  the 
governor  and  the  admission  valves,  the  exhaust  valves  are  let 
entirely  alone,  and  they  continue  their  work  unchanged.  It  will 
thus  be  seen  that  the  expansion  engine  makes  provision  for  the 
utmost  economy  in  the  use  of  steam,  and  with  the  automatic  fea- 
ture added  to  it,  provides  that  this  economy  shall  not  be  sacrificed 
for  the  purpose  of  regulating  the  speed. 

THE   GARDNER   SPRING   GOVERNORS. 

Construction*  —  Two  balls  are  rigidly  connected  to  the  upper 
ends  of  two  flat,  tapering,  steel  springs  —  the  lower  ends  of  the 
springs  being  secured  to  a  revolving  sleeve  which  receives  rotation 
through  mitre  gears  ;  links  connect  the  balls  to  an  upper  revolv- 
ing sleeve,  which  is  free  to  move  perpendicularly. 

The  valve  stem  passes  up  through  a  hollow  standard  upon  which 
the  sleeves  revolve,  and  is  furnished  with  a  suitable  bearing  in  the 
upper  sleeve  ;  the  closing  movement  of  the  valve  is  upward,  and 
is  obtained  in  the  following  manner :  The  balls  at  the  free  ends  of 
the  springs  furnish  the  centrifugal  force  and  the  springs  are  the 
main  centripetal  agency  (gravity  is  not  employed).  As  the  balls 
fly  outward,  under  the  centrifugal  influence,  they  move  in  a  curved 
horizontal  path  which  may  be  described  as  an  arc,  modified  by  a 
radius  of  changing  length  —  the  radius  being  represented  by  the 
length  and  position  of  the  springs  ;  the  links  represent  a  radius 
of  lesser  length, Awhile  the  sleeve  to  which  the  lower  ends  of  the 
links  are  pivoted,  being  free  to  rise  and  fall,  nullifies  the  effect  of 
the  links  in  determining  the  arc  in  which  the  balls  travel.  As  the 


342 


HANDBOOK    ON    ENGINEERING. 


balls  move  outward  in  their  peculiar  path,  the  sleeve  is  drawn  up- 
ward by  the  links,  and,  as  the  balls  move  inward,  the  sleeve  is 
pushed  downward.  The  change  of  speed  is  obtained  by  increas- 


THE  GARDNER  STANDARD  GOVERNOR— CLASS  "A" 

WITH  AUTOMATIC  SAFETY  STOP  AND  SPEEDER. 


ing  or  decreasing  the  centripetal  resistance,  and  accomplished  by 
the  action  of  a  spiral  spring  pivoted  against  the  lever,  and  by 
means  of  a  shaft  and  arm  against  the  valve-stem  in  the  direction 
to  open  the  valve  ;  a  thumb-screw  is  used  to  adjust  the  compres- 


HANDBOOK    ON    ENGINEERING. 


343 


sion.     A  convenient  Sawyer's  lever  is  attached  to  the  shaft,  and 
a  reliable  automatic  safety  stop  is  furnished  when  desired. 

The  cut  on  the  preceding  page  represents  the  Gardner  Standard 
Governor,  Class  "A." 

This  is  a  Gravity  Governor,  having  an  Automatic  Safety  Stop 
and  Speeder.  It  is  made  in  sizes  from  1J  inches  to  16  in., 
and  is  especially  adapted  to  the  larger  type  of  stationary  engines. 
In  action,  the  centrifugal  force  of  the  pendulous  balls  is  opposed 
by  the  resistance  of  a  weighted  lever,  the  speed  being  varied  by 
the  position  of  the  weight.  The  Automatic  Safety  Stop  is  very 
simple  in  construction  and  reliable  in  action.  It  is  accomplished 
by  allowing  a  slight  oscillation  of  the  shaft  bearing,  which  is  sup- 
ported between  centers  and  held  in  position  by  the  pull  of  the 
belt ;  a  projection  at  the  lower  part  of  the  shaft  bearing  supports 
the  fulcrum,  of  the  speed  lever.  If  the  belt  breaks  or  slips  off 
the  pulley,  the  support  of  the  fulcrum  is  forced  back,  so  as  to 
allow  the  fulcrum  to  drop  and  instantly  close  the  valve.  The 
valve  is  not  affected  by  steam  current  and  both  valve  and  seats 
are  made  of  special  composition,  that  effectually  resists  wear 
and  the  cutting  action  of  the  steam.  The  workmanship  is  of  the 
highest  class,  all  parts  being  made  by  the  duplicate  system,  with 
special  machinery. 

The  cut  on  the  following  page  represents  Class  "  B  "  Gov- 
ernor —  a  combination  of  the  gravity  and  spring  actions. 

They  are  made  in  sizes  from  f  to  10  inches  inclusive,  and  are 
adapted  to  all  styles  of  engines.  They  are  provided  with  Speeder 
and  Sawyer's  Lever,  but  are  not  automatic.  In  the  Class  "  li  " 
Governor  the  centrifugal  force  of  the  pendulous  balls  operates 
against  the  resistance  of  a  coiled  steel  spring,  inclosed  within  a 
case  and  pivoted  on  the  speed  lever  by  means  of  a  screw ;  the 
amount  of  compression  of  the  spring  can  be  changed  so  as  to  give 
a  wide  range  of  speed.  A  continuation  of  the  Speed  Lever  makes 
a  convenient  Sawyer's  hand  lever,  which  controls  the  valve  by 


344 


HANDBOOK    ON    ENGINEERING. 


means  of  a  cord.     Sizes  J  to  li  in.,  inclusive,  have  an  adjustable 
frame,  which  can  be  set  at  any  desired  angle  in  relation  to  the 


THE  GARDNER  STANDARD  GOVERNOR  —  CLASS  "B." 

valve  chamber.  The  valve  and  chamber  are  the  same  as  used  on 
Class  "  A  "  Governor,  and  they  are  made  with  the  same  care  and 
style  of  workmanship. 


HANDBOOK    ON    ENGINEERING. 


345 


CHAPTER     XIV. 
A  FEW  REHARKS   ON  THE  INDICATOR. 

The  steam-engine  indicator  is  an  instrument  designed  to  show 
the  steam  pressure  in  the  cylinder  at  all  points  in  the  stroke.  It 
consists  primarily,  of  a  piston  of  known  area  capable  of  moving 
in  a  cylinder  and  resisted  by  a  coil  spring  of  known  strength. 
To  this  piston  is  attached,  by  means  of  suitable  piston  rod  and 
levers,  a  pencil  capable  of  tracing  a  line  corresponding  to  the 
motion  of  the  indicator  piston.  This  line  is  traced  on  a  paper 
slip  attached  to  the  drum  of  the  indicator,  which  drum  is  con- 
nected to  some  moving  part  of  the  engine  in  such  a  way  as  to  have 
a  back  and  forward  movement,  coincident  with  the  steam  piston 
of  the  engine. 


By  referring  to  the  above  selected  view  of  an  indicator,  which 
is  generally  recognized  as  the  best  known,  the  construction  will  be 
readily  understood. 


Of-TH,   JA 


34()  HANDBOOK    ON    ENGINEERING. 

THE  USE  OF  THE  STEAH  ENGINE  INDICATOR  IN  SETTING 
VALVES  AND  THE  INVESTIGATION  OF  SOME  OF  THE  DE- 
FECTS BROUGHT  OUT  BY  THE  INDICATOR  CARDS. 

The  steam-engine  indicator  has  come  into  such  general  use 
that  to-day  there  are  but  few  men  running  engines  who  are  not 
familiar  with  its  construction  and  manner  of  attachment  to  en- 
gines, and  the  method  of  calculating  horse-power  from  cards. 
The  indicator  is  attached  to  pipes  tapped  into  the  cylinder  heads, 
or  into  the  barrel  of  the  cylinder  opposite  the  counterbore,  beyond 
the  travel  of  the  piston  rings.  The  indicator  consists  of  a  cylin- 
der with  piston  and  compression  spring  and  a  drum  attached  to  a 
coiled  spring,  used  for  returning  the  same.  The  pressure  of  steam 
on  the  piston  of  the  indicator  compresses  the  spring  above  it. 
The  motion  of  the  piston  is  carried  by  a  piston-rod  to  a  pencil 
motion,  which  multiplies  the  motion  of  the  spring  some  five  or  six 
times.  The  springs  "are  marked  20,  40,  80,  etc.  This  meaning 
that  80  Ibs.  pressure  per  square  inch  on  the  indicator  piston 
(or  whatever  the  spring  may  be  marked)  will  cause  the  pencil 
at  the  end  of  the  pencil-arm  to  move  an  inch.  The  pencil  marks 
on  paper,  which  is  fastened  on  a  drum.  This  drum  is  moved  by 
the  cross-head  of  the  engine,  through  some  form  of  reducing 
motion,  such  as  pantograph,  laz}r-tongs,  brumbo  pulley,  etc.  To 
obtain  the  horse-power,  we  first  need  the  mean  pressure  equiva- 
lent to  the  variable  pressure  on  the  card.  This  is  most  easily 
found  by  dividing  the  area  of  the  card  by  the  length,  giving  the 
height  of  a  rectangular  card  of  equivalent  area,  and  then  multi- 
plying this  height  by  the  scale  of  the  spring.  The  mean  effective 
pressure  per  square  inch  on  the  piston,  times  the  area  of  the  pis- 
ton in  square  inches,  times  the  speed  of  the  piston  in  feet  per 
minute,  divided  by  33,000,  gives  the  horse-power.  If  there  is  a 
loop  at  either  end  of  the  card,  the  area  of  this  loop  is  to  be  sub- 
tracted from  the  larger  area  before  finding  the  mean  height  of 


HANDBOOK    ON    ENGINEERING.  347 

the  card,  since  such  a  loop  represents  work  opposed  to  the  work- 
ing side  of  the  piston.  In  getting  areas  by  means  of  a  planimeter, 
no  attention  need  be  given  to  the  loops.  By  following  the  lines 
in  order,  as  drawn  by  the  indicator  pencil,  the  loops  will  be  sub- 
tracted from  the  main  card,  for  if  the  main  body  of  the  card  is 
traced  in  a  right-handed  rotation,  the  loops  will  be  traced  in  a 
left-handed  rotation. 

DIAGRAM  ANALYSIS. 

Figs*  \  and  2  are  from    throttling  engines  ;   the    former    repre- 
senting good  performances  for  that  class  of  engine,  and  the  latter, 


Fig.    1. 

in    some  respects  which  the  engineer  will  readily  recognize,  bad 
performances. 


'US  HANDBOOK    ON    ENGINEERING. 

Figs*  3,  4>  and  5,  are  from  automatics ;  Fig.  o  representing 
what  is  now  considered  rather  too  light  a  load  for  best  practical 
economy ;  Fig.  4  about  the  best  load,  and  Fig.  5  is  from  a  con- 
densing engine. 

Line  A  B  is  the  induction  line,  and  B  C  the  steam  line  ;  both 
together  representing  the  whole  time  of  admission. 

C  is  about  the  point  of  cut-off,  as  nearly  as  can  be  determined 
by  inspection.  It  is  mostly  anticipated  by  a  partial  fall  of  pres- 
sure due  to  the  progressive  closure  of  the  valve. 

The  usual  method  is,  to  locate  it  about  where  the  line  changes 
its  direction  of  curvature. 

C  D  is  the  expansion  curve.     1)  is  the  point  of  exhaust. 

D  E  is  the  exhaust  line,  which  begins  near  the  end  of  the  stroke 
and  terminates  at  the  end  of  the  stroke,  or,  at  latest,  before  the 
piston  has  moved  any  considerable  distance  on  its  return  stroke. 

The  principal  defect  of  Fig.  2  is,  that  this  line  occupies  nearly 
all  the  return  stroke.  E  F  is  the  back  pressure  line,  which,  in 
non-condensing  engines,  should  be  coincident  with,  or  but  little 
above,  atmospheric  pressure.  In  Fig.  5  it  is  below  the  atmos- 
pheric line  to  the  extent  of  the  vacuum  obtained  in  the  cylinder. 
Some  authorities  would  call  it  the  vacuum  line  in  Fig.  5  but  that 
name  properly  belongs  to  a  line  representing  a  perfect  vacuum. 

F  is  the  point  of  exhaust  closure  (slightly  anticipated  by  rise 
of  pressure)  and  F  A  the  compression  curve,  which,  joining  the 
admission  line  at  A,  completes  the  diagram  proper,  forming  a 
closed  figure. 

G  G  is  the  atmospheric  line  traced  when  the  piston  of  the  indi- 
cator is  subject  to  atmospheric  pressure,  above  and  below  alike. 
Some  pull  the  cord  by  hand  when  tracing  it,  to  make  it  longer 
than  the  diagram.  H  H  is  the  vacuum  line,  which,  when  re- 
quired, is  located  by  measurement  such  a  distance  below  the 
atmospheric  line  as  to  represent  the  atmospheric  pressure  at  the 
time  and  place,  as  nearly  as  can  be  ascertained.  The  mean 


HANDBOOK    ON    ENGINEERING.  349 

atmospheric  pressure  at  the  sea  level  is  14.7  pounds.  For  higher 
altitudes,  the  corresponding  mean  pressure  may  be  found  by 
multiplying  the  altitude  by  .00053,  and  subtracting  the  product 
from  14.7.  When  a  barometer  can  be  consulted,  its  reading  in 
inches  multiplied  by  .49  will  give  the  pressure  in  pounds. 


Fig.    2. 

1  is  the  clearance  line,  representing  by  its  distance  from  the 
nearest  point  of  the  end  of  the  diagram  at  the  admission  end,  as 
compared  with  the  whole  length,  the  whole  volume  of  clearance 
known  to  be  present.  Its  use  is  mainly  to  assist  in  constructing 
a  theoretical  expansion  curve  by  which  to  test  the  accuracy  of  the 
actual  one. 

Calculating  mean  effective  pressure*  —  Since  the  simplification 
and  popularization  of  the  planimeter,  no  engineer  who  has  occa- 


350 


HANDBOOK    ON    ENGINEERING. 


sion  to  compute  the."  indicated  horse-power  "  (1HP)  of  engines 
should    be    without    one ;     for,    if   properly  handled,  the  results 


obtained  by  them  are  more  accurate  and  more  quickly  obtained 
than  by  any  other  process.  The  diagram  is  pinned  to  a  smooth 
board  covered  with  a  sheet  of  smooth  paper,  the  pivot  of  the  leg 
pressed  into  the  board  at  a  point  which  will  allow  the  tracing  point 
to  be  moved  around  the  outline  of  the  diagram  without  forming 
unnecessarily  extreme  angles  between  the  two  legs,  and  a  slight 
indentation  made  in  the  line  at  some  point  convenient  for  begin- 
ning and  ending  ;  for  it  is  vitally  important  that  the  beginning  and 
ending  shall  be  at  exactly  the  same  point.  The  reading  of  the 
wheel  is  taken,  or  it  is  placed  at  zero,  and  the  tracing  point  is 


HANDBOOK    ON    ENGINEERING. 


351 


passed  carefully  around  the  diagram,  following  the  lines  as  closely 
us  possible,  moving  right-handed,  like  the  hands  of  a  watch.  The 
reading  obtained  (by  finding  the  difference  between  the  two,  if 
the  wheel  has  not  been  placed  at  zero)  is  the  area  of  the  diagram 
in  square  inches,  which,  multiplied  by  the  scale  of  the  diagram, 
and  divided  by  its  length  in  inches,  gives  the  mean  effective 
pressure. 

The  process  of  finding1  the  mean  effective  pressure  by 
ordinates* —  Divide  the  diagram  into  10  equal  parts  as  shown  by 
the  full  lines  in  Fig.  4 :  but  I  wish  to  call  attention  to  a  frequent 
mistake,  viz.. 


Fig.    4. 


making  all  the  spaces  equal.      The  end  ones  should  be    half    the 
width  of  the  others,  since  the  ordinates  stand   for  the   centers  of 


352  HANDBOOK    ON    ENGINEERING. 

equal  spaces.  Ten  is  the  most  convenient  and  usual  number  of 
ordinates,  though  more  would  give  more  accurate  results.  The 
aggregate  length  of  all  the  ordinates  (most  conveniently  measured 
consecutively  on  a  strip  of  paper)  divided  by  their  number,  and 
multiplied  by  the  scale  of  diagram,  will  give  the  mean  effective 


Fig.    5. 

pressure.  A  quick  way  of  making  a  close  approximation  to  the 
mean  effective  pressure  of  a  diagram  is,  to  draw  line  a  6,  Fig.  6, 
touching  at  a,  and  so  that  space  d  will  equal  in  area  spaces  c  and 
e,  taken  together,  as  nearly  as  can  be  estimated  by  the  eye. 
Then  a  measure,/,  taken  at  the  middle,  will  be  the  mean  effective 
pressure.  With  a  little  practice,. verifying  the  results  with  the 
planimeter,  the  ability  can  soon  be  acquired  to  make  estimates  in 


HANDBOOK    ON    ENGINEERING. 


353 


this  way  with  only  a  fraction  of  a  pound  of  error  with  diagrams 
representing  some  degree  of  load.  With  very  high  initial  pres- 
sure and  early  cut-off,  it  is  not  so  available. 


Fig.  6. 

The  indicated  horse-power.  —  IHP  is  found  by  multiplying 
together  the  area  of  the  piston  (minus  half  the  area  of  the  piston- 
rod  section,  when  great  accuracy  is  desired),  the  mean  effective 
pressure  and  the  travel  of  the  piston  in  feet  per  minute,  and 
dividing  the  product  by  33,000.  It  is  sometimes  convenient  to 
know  the  HP  constant  of  an  engine,  which  is  the  HP  for  one 
revolution  at  one  pound  mean  effective  pressure.  This  multiplied 
by  the  mean  effective  pressure,  and  by  its  number  of  revolutions 
per  minute,  gives  the  IHP. 


THEORETICAL  CURVE. 

Testing  expansion  curves.  —  It  is  customary  to  assume  that 
steam,  in  expanding,  is  governed  by  what  is  known  as  Mariotte's 
law,  according  to  which  its  volume  and  pressure  are  inversely  pro- 

23 


354 


HANDBOOK    ON    ENGINEERING. 


portioual  to  each  other.  Thus,  if  a  cubic  loot  of  steam  at,  say, 
100  pounds  pressure  be  expanded  to  2  cubic  feet,  its  pressure 
will  fall  to  50  pounds,  and  proportionately  for  all  other  degrees 
of  expansion.  The  pressures  named  are  "  total  pressures  ;  "  that 
is,  they  are  reckoned  from  a  perfect  vacuum.  A  theoretic  ex- 
pansion curve  which  will  conform  to  the  above  theory  may  be 


\ 


K 


10 


Fig.  7. 


traced  by  the  following  method:  Referring  to  F'^.  7,  having 
drawn  the  clearance  and  vacuum  lines  as  before  explained,  draw 
any  convenient  number  of  vertical  lines,  1,  2,  3,  4,  5,  etc.,  at 
equal  distances  apart,  beginning  with  the  clearance  line  and  num- 
ber them  as  shown.  Decide  at  what  point  in  the  expansion  curve 


HANDBOOK    ON    ENGINEERING. 

of  the  diagram  you  wish  the  theoretic  curve  to  coincide  with  it. 
Suppose  you  choose  line  10,  on  which  you  find  the  indicated  pres- 
sure to  be  25  pounds.  Multiply  this  pressure  by  the  number  of 
the  line  (10)  and  divide  the  product  (250)  by  the  numbers  of 
each  of  the  other  lines  in  succession.  The  quotients  will  be  the 
pressures  to  be  set  off  in  the  lines.  Thus,  250  divided  by  1)  gives 
27.7,  the  pressure  on  line  9  ;  and  so  for  all  the  others.  The 
same  curve  may  also  be  traced  by  several  geometric  methods,  one 
of  which  is  as  follows,  referring  to  Fig.  8 :  - 


E 


Fig.  8. 

Having  drawn  the  clearance  and  vacuum  lines  as  before, 
select  the  desired  point  of  coincidence,  as  a,  from  which  draw  the 
perpendicular  a  A.  Draw  A  B  at  any  convenient  height  above  or 
near  the  top  of  the  diagram,  and  parallel  to  the  vacuum  line  D  C. 
From  A  draw  A  C  and  from  a  draw  a  b  parallel  to  D  (7.  and  from 


356  HANDBOOK    ON    ENGINEERING. 

its  intersection  with  A  B,  erect  the  perpendicular  b  r,  locating  the 
theoretical  point  of  cut-off  on  A  B.  From  any  convenient  num- 
ber of  points  in  A  B  (which  may  be  located  without  measurement) 
as  E,  F,  G,  H,  draw  lines  to  0,  and  also  drop  perpendiculars  E  e, 
F  f,  G  g,  Hli,  etc.  From  the  intersection  of  E  C  with  b  c,  draw  a 
horizontal  to  e,  and  the  same  for  each  of  the  other  lines  F  C, 
G  (7,  H  C;  establishing  points  e,/,  </,  ft,  in  the  desired  curve. 
Any  desired  number  of  points  may  be  found  in  the  same  way. 
But  this  curve  does  not  correctly  represent  the  expansion  of 
steam.  It  would  do  so  if  the  steam  during  expansion  remained 
or  was  maintained  at  a  uniform  temperature ;  hence,  it  is  called 
the  isothermal  curve,  or  curve  of  same  temperature.  But,  in  fact, 
steam  and  all  other  elastic  fluids  fall  in  temperature  during  expan- 
sion, and  rise  during  compression;  and  this  change  of  temperature 
augments  the  change  of  pressure  slightly ;  so  that  if,  as  before 
assumed,  a  cubic  foot  of  steam  at  100  pounds  total  pressure  be 
expanded  to  two  cubic  feet,  the  temperature  will  fall  from  nearly 
328°  to  about  278°,  and  the  pressure  instead  of  falling  to  fifty 
pounds,  will  fall  a  trifle  below  48  pounds.  A  curve  in  which  the 
pressure  due  to  the  combined  effects  of  volume  and  resulting 
temperature  is  represented,  is  called  the  adiabatic  curve,  or  curve 
of  no  transmission  ;  since,  if  no  heat  is  transmitted  to  or  from  the 
fluid  during  change  of  volume,  its  sensible  temperature  will 
change  according  to  a  fixed  ratio,  which  will  be  the  same  for  the 
same  fluid  in  all  cases.  I  need  not  attempt  to  give  any  of  the 
usual  methods  of  tracing  the  adiabatic  curve,  since  the  isothermal 
curve  is  the  one  generally  used  for  that  purpose.  And  while  it  is 
incorrect  in  that  it  does  not  show  enough  change  or  pressure  for  a 
given  change  of  volume,  the  great  majority  of  actual  diagrams  are 
still  more  incorrect  in  the  same  direction ;  so  that  when  a  diagram 
conforms  to  it  as  closely  as  the  one  used  in  these  illustrations,  it 
is  considered  a  remarkably  good  one.  A  sufficiently  close 
approximation  to  the  adiabatic  curve  to  enable  the  non-profes- 


HANDBOOK    ON    ENGINEERING.  357 

sional  engineer  to  form  an  idea  of  the  difference  between  the  two, 
may  be  produced  by  the  following  process :  Taking  a  similar 
diagram  to  those  used  for  the  foregoing  illustrations,  we  fix  on  a 
point  A  near  the  terminal,  where  the  total  pressure  is  25  pounds. 
As  before,  this  point  is  chosen  in  order  that  the  two  curves  may 
coincide  at  that  point.  Any  other  point  might  have  been  chosen 
for  the  point  of  coincidence  ;  but  a  point  in  that  vicinity  is  generally 
chosen  so  that  the  result  will  show  the  amount  of  power  that 
should  be  obtained  from  the  existing  terminal.  This  point  is  3.3 
inches  from  the  clearance  line,  and  the  volume  of  25  pounds  is 
996  ;  that  is,  steam  at  that  pressure  has  996  times  the  bulk  of 
water.  Now,  if  we  divide  the  distance  of  A  from  the  clearance 
line  by  996,  and  multiply  the  quotient  by  each  of  the  volumes  of 
the  other  pressures  indicated  by  similar  lines,  the  products  will  be 
the  respective  lengths  of  the  lines  measured  from  the  clearance 
line,  the  desired  curve  passing  through  their  other  ends.  Thus, 
the  quotient  of  the  first,  or  25-pound  pressure  line  divided  by 
996  is  .003313;  this  multiplied  by  726,  the  volume  of  25-pound 
pressure,  gives  2.4,  the  length  of  the  25-pound  pressure  line  ;  and 
so  on  for  all  the  rest. 

Fig*  9  shows  a  card  taken  from  a  Corliss  engine,  running  at  a 
speed  of  about  ninety  revolutions  per  minute.  On  account  of  the 
slow  speed  and  the  quick 
admission  obtained  by  this 
form  of  valve  gear,  but  lit- 
tle compression  is  needed. 
For  high  speed  engines, 
there  is  much  more  com- 
pression. At  high  speeds, 

the  expansion  line  of    the    — — —  •  •     • — 

indicator  card,  instead  of 

being  a  smooth  curve  like  that  shown  in  Fig.  9,  is  often  a  wavy 

line,  due  to  oscillations  of  the  spring  in  the  indicator. 


358  HANDBOOK    ON     ENGINEERING. 

Fig*  10  represents  what  is  called  a  stroke  card.     The  indicator 

shows  us  the  pressure  on 
one  side  of  the  piston  for 
a  revolution.  When  we 
calculate  the  horse-power 
from  a  card,  we  are  as- 
suming that  the  back  pres- 
sure and  compression 
line  on  the  other  side  of 


"   the  piston  are  the  same  as 
FIST.  10. 

shown  on  the  card.    This 

may  or  may  not  be  the  case.  In  calculating  the  total  horse-power 
for  the  two  ends  of  the  cylinder,  any  error  from  this  cause  affect- 
ing the  calculation  for  one  end  of  the  cylinder,  will  be  nearly 
balanced  by  an  opposite  error  in  the  calculations  for  the  other  end, 
so  that  the  final  result  is  practically  correct.  If  it  were  not  for 
the  piston-rod  making  the  area  of  one  side  of  the  piston  smaller 
than  on  the  other,  there  would  be  absolutely  no  error  arising 
from  this.  The  stroke  card  shows  the  pressure  on  opposite 
sides  of  the  piston  at  all  points  of  the  stroke.  The  difference 
between  the  lines  at  any  point  is  the  effective  push  per  square 
inch.  This  card  is  constructed  by  using  the  steam  and  expan- 
sion lines  of  the  card  from  one  end,  and  the  back  pressure 
and  compression  lines  for  the  same  stroke,  from  the  card  taken 
on  the  other  end.  In  constructing  diagram  for  very  accurate 
work,  the  ratio  of  the  areas  of  the  two  sides  of  the  piston  have 
to  be  considered ;  the  pressure  above  the  atmosphere  for  one 
side  being  multiplied  by  this  ratio.  It  will  be  seen  that  up  to 
the  point  of  cut-off,  the  difference  of  pressure,  or  effective  pres- 
sure, is  nearly  constant ;  this  difference  grows  less,  due  to  the 
drop  along  the  expansion  curve,  till  at  the  point  where  the 
two  lines  cross,  the  pressure  on  the  two  sidts  balances.  Be- 
yond this  point,  the  pressure  exerted  to  hold  the  piston  back 


HANDBOOK    ON    EXCS1XKKKI  N<! 


is  greater  than  that  exerted  to  push  it  ahead.  The  energy  stored  in 
the  fly-wheel  during  the  first  part  of  the  stroke  is  given  out  here 
near  the  end  of  the  stroke  to  help  the  engine  over  the  dead  point. 

STEAfl  CHEST  CARDS. 

By  attaching-  one  indicator  to  the  steam  chest  of  an  engine, 
and  another  to  one  end  of  the  cylinder,  it  can  be  seen 
whether  the  pipes  and  port 5  are  of  sufficient  size.  A 
sloping  steam  line  on  an  indicator  card  may  be  due  to  too 
small  a  steam  pipe,  or  too 
small  steam  ports,  or  to 
both  of  these  combined. 
This  does  not  apply,  of 
course,  to  engines  using 
throttling  governors. 

Fig*  \  \  shows  the  effect 
of  too    small  steam  pipe. 

When  steam   is   admitted  

to  the  cylinder,  there  is  a      Fig.  11.  Steam  Chest  on  Forward 


drop   in   pressure   in   the 


Stroke. 

chest.    This  drop  becomes  greater  in  amount  as  the  speed  of  the 

piston  increases.  At  cut- 
off, the  flow  of  steam  into 
the  cylinder  stops,  then 
the  pressure  in  the  chest 
reaches  boiler  pressure. 
If  there  is  no  great  drop 
in  the  line  on  the  steam 
chest  card,  and  a  consid- 
erable drop  in  the  steam 


Fig.  12.  Steam  Chest  Card  on 
Forward  Stroke. 


too  small. 


line  of  the  card,  it  would 
mean   that  the    ports  are 
Such   a  case  is   shown   by  Fig.    12. 


360 


HANDBOOK    ON    ENGINEERING. 


Fig.  13.  Steam  Chest  Card  on 
Forward  Stroke. 


If  there  is  a  drop  in 
the  chest  line  up  to  cut- 
off, and  a  still  greater 
drop  in  the  steam  line 
of  the  card,  it  would 
indicate  that  both  the 
steam  ports  and  the 
steam  pipe  were  too 
small.  Fig.  13  shows 
such  a  case. 


ECCENTRIC  OUT  OF  PLACE. 

Fig's*  14,  15,  16,  and  17,  show  cards  taken  from  a  Corliss  p]n- 
gine  having  the  eccentric  out  of  adjustment.  Similar  cards  would 
be  obtained  from  any  en- 
gine having  all  the  valves 
moved  by  one  eccentric. 
The  plain  slide  valve  and 
the  locomotive,  especially 
in  full  gear,  would  give 
similar  cards  for  the  same 
derangements  of  eccen- 
tric. 

Fie'*  14  was  taken  with  ""     ~ ~~.        ,   1K  """ 

8*  Figs.  14  and   15. 

the  eccentric  a  trifle  less 

than  90°  ahead  of  the  crank,  or  about  20°  behind  where  it  belongs 
on  this  particular  engine. 

Fig*  15  shows  the  eccentric  moved  too  far  ahead  of   the  crank. 

By  comparison  with  Fig.  9,  it  will  be  seen  that  moving  the 
eccentric  back  makes  all  the  events  of  the  stroke,  such  as  admis- 
sion, release  and  compression  and  cut-off,  in  the  case  of  engines 
without  automatic  cut-off  governor,  come  later ;  while  moving 
the  eccentric  ahead  brings  these  events  earlier. 


HANDBOOK    ON    ENGINEERING. 


361 


Figs.  \6  and  17  are  similar  to  Figs.  14' and  15,  the  only  differ- 
ence being  that"  eccentric  is  moved  a  greater  distance  out  of  place. 

In  Fig*  \6  the  admission 
is  very  late.  Release  does 
not  occur  until  after  the 
piston  has  started  on  the 
return  stroke,  the  steam, 
until  released,  being  com- 
pressed back  along  the  ex- 
pansion curve.  This  com- 
pression is  always  a  trifle 

Figs.   16  and  17. 
below   the   expansion  line, 

due  to  the  fact  that  some  of  the  steam  has  condensed  in  the 
interval  between  the  end  of  the  stroke  and  the  release. 

Fig*  17  shows  too  much  compression  and  too  early  a  release. 
Steam  is  compressed  above  boiler  pressure  in  the  cylinder,  when 
the  valve  lifts  and  the  steam  escapes  into  the  chest. 

Cards  like  Figs.  14  and  15  are  very  common. 

ECCENTRIC    CARDS. 

As  small  distances  near  the  ends  of  the  indicator  cards  repre- 
sent a  large  angular  motion  of  the  crank,  the  events  occurring  at 
the  ends  of  the  card  are  so  squeezed  together  that  it  is  hard  to 
tell  from  the  card  just  what  any  peculiarity  in  the  lines  may  be 
due  to.  The  eccentric  rod  working  the  valves  of  the  engine  will 
be  moving  at  its  greatest  speed  when  the  crank  is  near  the  centers 
and  the  piston  near  the  ends  of  the  stroke ;  since  the  eccentric  is 
about  90°  ahead  of  the  crank.  If  the  motion  of  the  indicator 
drum  is  taken  from  the  eccentric  rod  instead  of  the  cross-head,  the 
card  will  be  changed  in  shape,  compression  and  release  coming 
near  the  middle  of  the  card,  and  being  spread  out  over  consider- 
able length,  the  cut-off,  expansion  and  back  pressure  lines  coming 
near  the  ends  of  the  card. 


HANDBOOK    ON    ENGINEERING. 


Fig*  18  gives  a  steam  card  drawn,  assuming  that  the  expansion 
and  compression  lines  are  hyperbolic.    The  eccentric  card  for  this 

had  been  plotted,  and  cor- 
responding points  marked 
with  the  same  letters.  The 


F  F 


Fig.  18. 


Fig.   19. 


compression  curve,  extending  from  F  to  A,  is  a  double  curve. 
Admission  occurs  at  A,  cut-off  at  7J,  release  at  G',  and  compres- 
sion at  F. 

Figs.  \9  and  20  show  cards  taken  from  an  engine  having  tight 
valves  and  a  tight  piston.     Corresponding  points  on  the  two  cards 

are  lettered  the  same.  For  a 
cut-off  later  than  half  stroke, 
the  steam  line  on  the  eccen- 
tric card  doubles  on  itself,  as 
shown  in  Figs.  21  and  22. 

The  peculiar  bend  shown 
by  the  dotted  lines  on  coin- 


Fig.  20. 

pression  curve  of  the  steam  card, 
Fig.  18,  is  developed  on  the 
eccentric  card  into  a  well  marked 
flat  place.  Evidently  this  rep- 
resents a  loss  of  pressure  at  this 
point,  which  may  be  attributed 
to  one  or  more  of  three  causes : 
first,  leakage  by  the  piston ; 


Fig.  21. 
second,  leakage  by  the  exhaust  valves ;  third,  a  rapid  condensa- 


HANDBOOK    OX    ENGINEERING.  363 

tion  of  steam.  If  ;i  leakage,  it  is  probable  that  there  is  steam 
blowing  by  all  through  the  stroke. 
Near  the  end  of  the  stroke  the  pis- 
ton is  moving  at  so  slow  a  rate  that 
the  leakage  overbalances  the  com- 
pression. It  frequently  happens 

that  the  pressure  drops  off  at  the          

end    of    compression,    making   the  Fig.  22. 

upper  end  of  the  compression  line 

resemble  an  inverted  letter  U.  If  the  leakage  is  by  the  piston, 
it  will  appear  or  may  be  made  to  appear  near  release,  as  will  be 
explained  later.  The  effect  of  compressing  steam  is  to  dry  it, 
or,  if  dry  already,  to  superheat  it.  While  it  may  be  possible  in 
some  cases  for  some  of  the  drop  here  to  be  due  to  .condensation, 
in  the  majority  of  cases  leakage  is  the  trouble. 

Fig.  23  shows  the  effect  of  a  bad  leakage  by  the  piston.     This 
leakage  is  made  evident  by  the  appearance  of  the  upper  end  of 

the  compression  curve 
and  by  the  increase  in 
pressure  .along  the  expan- 
sion line  just  before  re~ 
lease.  By  referring  to 
the  stroke  card,  it  will  be 
seen  that  near  this  point 
the  pressures  on  the  oppo- 
site side  of  the  piston  are 

the  greater,  so  that  the  leakage  is  now  into  the  side  on  which  the 
card  is  being  taken.  Unless  compression  on  one  side  comes 
earlier  than  release  on  the  other  side,  this  method  would  fail. 
In  most  engines  the  valves  are  set  so  that  compression  does 
come  earlier,  and  all  four  valve  engines  can  be  easily  set  so 
as  to  delay  release  on  one  end,  and  to  hasten  compression  on  the 
other  end.  In  the  case  of  a  Corliss  engine,  this  means  simply 


364 


HANDBOOK    ON    ENGINEERING1 


the  changing  the  length  of  the  rods  leading  from  the  wrist  plate 
to  the  valve  arm.  This  change  can  be  made  with  the  engine  run- 
ning. It  is  possible  that  a  card  like  Fig.  23  might  be  obtained 
from  a  four-valve  engine  having  a  leaky  steam  valve  on  one  end 
and  a  leaky  exhaust  valve  on  the  other  end. 

Fig.  24  represents  the  head  end  and  the  crank  end  cards 
taken  from  a  plain  slide  valve  engine.  The  valve  has  equal 
steam  laps  and  equal  exhaust  laps.  The  only  trouble  in  this  case 


Fig.  24. 

is  that  the  valve  spindle  is  too  short.  Shortening  the  valve  spin- 
dle decreases  the  outside  lap  of  the  valve  and  increases  the  inside 
lap  for  the  head  end  side,  and  increases  the  outside  lap  and  de- 
creases the  inside  lap  for  the  crank  end  side.  As  will  be  seen  by 
the  cards,  the  head  end  has  the  cut-off  lengthened,  the  release 
delayed,  and  the  compression  hastened;  the  crank-end  has  the 
cut-off  shortened,  the  release  hastened,  and  the  compression  de- 
layed. If  the  valve  spindle  were  too  long  the  cards  shown  would 
be  interchanged,  the  crank  end  card  being  the  one  marked  head 
end. 

THE  STEAM  ENGINE  INDICATOR. 

Benefits  derived  and  information  ascertained  from  its  use*  — 
The  benefits  derived,  and  the  information  ascertained  from  the 
use  of  the  steam-engine  indicator  are- varied  and  important. 


HANDBOOK    ON    ENGINEERING.  365 

"  The  office  of  the  indicator  is  to  furnish  a  diagram  of  the 
action  of  the  steam  in  the  cylinder  of  an  engine  during  one  or 
more  revolutions  of  the  crank,  from  which  is  deduced  the  follow- 
ing data :  Initial  pressure  in  cylinder  ;  piston  stroke  to  cut-off  ; 
reduction  of  pressure  from  commencement  of  piston  stroke  to  cut- 
off ;  piston  stroke  to  release ;  terminal  pressure ;  gain  in  econ- 
omy due  expansion ;  counter  pressure,  if  engine  is  worked, 
non-condensing ;  tacuum  as  realized  in  the  cylinder,  if  engine  is 
worked  condensing ;  piston  stroke  to  exhaust  closure,  usually 
reckoned  from  zero  point  of  stroke ;  value  of  cushion ;  effect  of 
lead  and  mean  effective  pressure  on  the  piston  during  complete 
stroke.  The  indicator  diagram,  when  taken  in  connection  with 
the  mean  area  and  stroke  of  piston  and  revolution  of  crank 
for  a  given  length  of  time,  enables  us  to  ascertain  the  power  de- 
veloped by  engine ;  and  when  taken  in  connection  with  the  mean 
area'  of  piston,  piston  speed  and  ratio  of  cylinder  clearance, 
enables  us  to  ascertain  the  steam  accounted  for  by  the  engine. 

"  The  mean  power  developed  by  engine  compared  with  the 
steam  delivered  by  boilers,  furnishes  cost  of  power  in  steam, 
and  when  compared  with  the  coal,  furnishes  cost  of  the  power  in 
fuel. 

"  The  diagram  also  enables  us  to  determine  with  precision  the 
size  of  steam  and  exhaust  ports  necessary,  under  given  conditions, 
to  equalize  the  valve  functions  ;  to  measure  the  loss  of  pressure 
between  boiler  and  engine ;  to  measure  the  loss  of  vacuum  be- 
tween condenser  and  cylinder ;  to  determine  leaks  into  and  out 
of  the  cylinder ;  to  determine  relative  effects  of  jacketed  and 
un jacketed  cylinders ;  and  to  determine  effects  of  expansion  in 
one  cylinder,  and  in  two  or  more  cylinders." 

TO  TAKE  A  DIAGRAM. 

Connecting-cord*  —  The  indicator  should  be  connected  to  the 
engine  cross-head  by  as  short  a  length  of  cord  as  possible.  Cord 


66  HANDBOOK    ON    ENGINEERING. 

having  very  little  stretch,  such  as  accompanies  the  instrument, 
should  be  used  ;  and  in  cases  of  very  long  lengths,  wire  should 
be  used.  The  short  piece  of  cord  connected  with  the  indicator  is 
furnished  with  a  hook;  and  at  the  end  of  the  cord,  connected 
with  the  engine,  a  running  loop  can  be  made  by  means  of  the 
small  plate  sent  with  each  instrument ;  by  which  the  cord  can  be 
adjusted  to  the  proper  length,  and  lengthened  or  shortened  as 
required. 

Selecting-  a  spring,  —  It  is  not  advisable  to  use  too  light  a 
spring  for  the  pressure.  Two  inches  are  sufficient  for  the  height 
of  diagram,  and  the  instrument  will  be  less  liable  to  damage  if 
the  proper  spring  is  used.  The  gauge  pressure  divided  by  2 
will  give  the  scale  of  spring  to  give  a  diagram  two  inches  high  at 
that  pressure. 

To  attach  a  card*  —  This  may  be  done  in  a  variety  of  ways, 
either  by  passing  the  ends  of  it  under  the  spring  clips,  or  by 
folding  one  end  under  the  left  clip,  and  bringing  the  other  end 
around  under  the  right ;  but,  whatever  method  is  applied,  care 
should  be  taken  to  have  the  card  rest  smoothly  and  evenly  on  the 
paper  drum.  Now  attach  the  cord  from  the  reducing  motion  to 
the  engine  ;  but  be  certain  the  cord  is  of  the  proper  length,  so  as 
to  prevent  paper  drum  from  striking  the  inner  stop  in  drum 
movement  on  either  end  of  the  stroke. 

Tension  of  drum  spring.  —  The  tension  of  the  drum  spring 
should  be  adjusted  according  to  the  speed  of  the  engine ;  in- 
creasing for  quick  running,  and  loosening  for  slower  speeds. 

The  steam  should  not  be  allowed  into  the  indicator  until  it  has 
first  been  allowed  to  escape  through  the  relief  on  side  of  cock,  to 
see  if  is  clean  and  dry.  If  clean  and  dry,  allow  it  into  the  indi- 
cator, and  allow  piston  to  play  up  and  down  freely. 

Before  taking  diagram,  turn  the  handle  of  cock  to  a  horizontal 
position,  so  as  to  shut  off  steam  from  piston,  and  apply  pencil  to 
the  paper  to  take  the  atmospheric  line. 


HANDBOOK    ON    ENGINEERING. 


367 


In  applying  pencil  to  the  card,  always  use  the  horn-handle 
screw,  to  regulate  pressure  of  pencil  upon  paper  to  produce  as 
line  a  line  as  possible.  After  the  atmospheric  line  is  taken,  turn 
on  steam,  and  press  the  pencil  against  card  during  one  revolution. 

When  the  load  is  varying,  and  the  average  horse-power  re- 
quired, it  is  better  to  allow  the  pencil  to  remain  during  a  number 
of  revolutions,  and  to  take  the  mean  effective  pressure  from  the 
card . 


Fig.   25. 

Fig.  25  was  taken  from  a  Russell  engine  13"x20",  running 
205  revolutions  per  minute,  boiler  pressure  98  Ibs.,  scale  of  indi- 
cator 60  Ibs.  Duty,  electric  lighting. 

After  sufficient  number  of  diagrams  have  been  taken,  remove 
the  piston,  spring,  etc.,  from  the  indicator,  while  it  is  still  upon 
the  cylinder ;  allow  the  steam  to  blow  for  a  moment  through  the 
indicator  cylinder;  and  then  turn  attention  to  the  piston,  spring, 
and  all  movable  parts,  which  may  be  thoroughly  wiped,  oiled  and 
cleaned.  Particular  attention  should  be  paid  to  the  springs,  as 
their  accuracy  will  be  impaired  if  they  are  allowed  to  rust ;  and 
great  care  should  be  exercised  that  no  grit  or  substance  be  intro- 
duced to  cut  the  cylinder,  or  scratch  the  piston.  Be  careful 


368 


HANDBOOK    ON    ENGINEERING 


always  not  to  bend  the  steel  bars  or  rods.  The  heat  of  the  steam 
blown  through  the  cylinder  of  the  indicator  will  be  found  to  have 
dried  it  perfectly,  and  the  instrument  may  be  put  together  with 
the  assurance  that  it  is  all  ready  for  use  when  required.  Other 
items  of  precaution  should  be  borne  in  mind.  Any  engineer 
can  easily  repeat  this  operation  without  further  instruction. 


Fig.   26. 

Fig.  26  was  taken  from  a  Russell  engine  16"x24",  running 
157  revolutions  per  minute,  boiler  pressure  70  Ibs.,  scale  of  indi- 
cator 40  Ibs.  Duty,  flouring  mill. 


FRICTION  INDICATION.  FULL  LOAD-  INDICATION. 

HARRISBURG  IDEAL  SIMPLE  SINGLE  VALVE  ENGINE. 
Fig.  27.  Fig.  28. 


HANDBOOK    ON    ENGINEERING. 


3(59 


GRADUATED  LOAD 
INDICATION. 


EXTREME  LOAD  VARIATION 
INDICATION. 


HARRISBURG  IDEAL  SIMPLE  SINGLE  VALVE  ENGINE.") 
Fig.  29.  Fig.  30. 


HIGH  PRESSURE  INDICATION.  Low  PRESSURE  INDICATION. 

HARRISBURG  IDEAL  COMPOUND  SINGLE  VALVE  ENGINE. 


Fig.  31. 


Fig.  32. 


FRICTION  INDICATION.  FULL  LOAD  INDICATION. 

HARRISBURG  STANDARD  SIMPLE  SINGLE  VALVE  ENGINE. 


Fig.  33. 


Fig.  34. 


370 


HANDBOOK    ON    ENGINEERING. 


FRICTION  INDICATION.  FULL  LOAD  INDICATION. 

HARRJSP.URG  STANDARD  SIMPLE  FOUR-VALVE  ENGINE. 


Fig.  35. 


Fig.  36. 


HIGH  PRESSURE  INDICATION.  Low.  PRESSURE  INDICATION* 

HARRISBUKG  STANDARD  COMPOUND  FOUR-VALVE  ENGINE. 


Fig.  37. 


Fig.  38. 


Figs*  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  37  and  38  are 
cards  taken  from  the  Harrisburg  Ideal  and  Standard  Engines. 
An  engineer  will  see  from  these  cards  the  kind  of  card  he  should 
get  from  a  high  speed  engine  of  this  class. 

Fig.  39  iy  from  a  Frick  Corliss  Engine,  driving  a  Frick  Com- 
pressor: — 

Steam   Cylinder Ii)"x28". 

Steam 1)5  Ibs. 

Revs 58 

Cond.  Press 164  Ibs. 

Back  Press,  .      .      .      ,  27    Ibs. 


HANDBOOK    ON    ENGINEERING, 


371 


Snpine,  19"  x  28". 
Steam,  95  Ibs. 
Revs.  58  Ibs. 
Cond.  Press. ,  164  Ms. 
Back  Press..  27  &5; 


Fig.  39. 


INDICATOR  DIAGRAMS  FROM  50-TON  "ECLIPSE" 
MACHINE. 


/? 

12$"  s  28". 
Seate.  120/fo. 


Fig.   40. 
i^.  40  is  R.  Hand  Pump.      12 -i"  x  28".     Scale,  120  Ibs. 


372 


HANDBOOK    ON    ENGINEERING, 


L.-Hand  Pump. 
12*"  x  28". 
Scale,  120  Ms. 


Fig.  41. 
Fig.  41  is  L.  Hand  Pump.     27J"  x  28".     Scale,  120  Ibs. 


Engine,  30"  x  36" 
Steam,  75  Ibs. 
Revs.  44 

Cond.  Press.,  162  Ibs. 
Back  Press.,  \Q  lb». 


Fig.  42. 

Figs*  42,  43  and  44   are  diagrams    from    a    100-ton   "Eclipse 
Machine." 


HANDBOOK    ON    ENGINEERING. 


373 


INDICATOR  DIAGRAMS  FROM  100-TON  "JECUPSE," 
MACHINE. 


R.  Hand  Pump* 
17"  x  36". 
Scale,  80  Iba 


Fig.  43. 


L.  Hand  Pump, 
17"  x  36". 
Scale.  80  163 


Fig.  44. 


374: 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK    ON    ENGINEERING. 


375 


It  will  be  interesting  to  note  that  when  the  eccentric  is  simply 
moved  forward  or  backward  around  the  shaft  by  the  action  of  the 
governor,  all  the  events  of  the  stroke  —  admission,  release,  cut-off 
and  compression  —  will  be  hastened  or  retarded  together  ;  but  if 
the  eccentric  be  so  designed  that  the  governor  will  shift  it  across 
the  shaft  instead  of  around  it,  the  admission  and  release  will  be 
effected  differently,  and  in  the  opposite  direction  from  the  cut-off 
and  compression.  If,  for  example,  the  cut-off  is  made  to  occur 
earlier  in  the  stroke,  the  compression  will  occur  earlier  also,  but 
the  admission  and  release  will  occur  later  instead  of  earlier.  By 
combining  the  two  movements  of  the  eccentric  and  having  the 
governor  move  it  partly  around  and  partly  across  the  shaft,  it  is 
possible  to  keep  the  admission  and  release  nearly  constant,  while 
the  cut-off  and  compression  vary.  This  result  is  attained  to  a 
certain  extent  in  the  best  single-valve  engines.  Besides  these  two 
types,  there  are  numerous  other  styles  of  engines  in  which  the 
point  of  cut-off  is  varied  automatically.  Instead  of  a  shaft  gov- 
ernor with  a  shifting  eccentric,  a  weighted  pendulum  governor  is 
sometimes  employed  to  operate  the  link,  or  radius  rod  of  some 
one  of  the  various  link  motions.  Sometimes  there  are  separate 
admission  and  exhaust  valves,  the  former  being  under  the  con- 
trol of  a  shaft  governor,  and  the  latter  operated  by  a  fixed  eccen- 
tric, so  that  the  points  of  admission  and  cut-off  only  are  varied, 
while  the  points  of  release  and  compression,  which  depend  upon 
the  exhaust  valve,  remain  fixed.  There  are  a  great  many  modifi- 
cations of  the  Corliss  engine,  as  originally  constructed  by 
Geo.  H.  Corliss,  and  there  are  many  engines  which,  while  not  re- 
sembling the  Corliss  engine,  have  some  arrangement  whereby  the 
cut-off  valves  are  tripped. 

On  pages  374  and  376  is  a  collection  of  diagrams  which 
illustrate  very  nicely  the  peculiarities  and  difference  in  the  action 
of  throttling  and  automatic  engines.  The  four  diagrams  on 
page  374  were  taken  from  a  Bail  automatic,  in  an  electric  light 


37(3 


HANDBOOK    ON    ENGINEERING. 


HANDBOOK  ON  P^NGINEERING.  377 

station.  The  first  diagram  was  taken  late  in  the  afternoon  when 
the  engine  was  started  and  before  any  load  was  thrown  on  to  the 
machine,  and  the  three  succeeding  cards  were  taken  at  intervals 
later  in  the  evening  as  the  number  of  lights  increased  and  the 
load  became  heavier.  Two  or  three  important  points  are  to  be 
noticed  in  connection  with  these  diagrams.  First,  the  initial 
pressure  of  the  steam  at  the  point  of  admission  is  very  nearly  the 
same  in  all  four  cards,  the  slight  variations  being  due  chiefly  to  a 
variation  in  the  boiler  pressure.  Second,  the  length  of  the  cut-off 
increases  with  the  load.  The  compression  also  becomes  later  as 
the  cut-off  lengthens,  and  while  there  is  also  a  change  in  the  points 
of  admission  and  release,  it  is  not  as  marked  as  the  changes  in  cut- 
off and  compression,  for  reasons  that  have  already  been  explained. 

Taking  the  cards  on  page  376,  we  have  four  excellent  examples 
of  the  action  of  a  throttling  engine.  These  cards  are  from  a 
Dickson  engine,  taken  at  the  same  station  and  under  the  same 
conditions  as  the  Ball  engine  cards,  with  the  exception  that  in 
this  case  both  head  and  crank-end  diagrams  were  taken  on  the 
same  cards,  while  only  the  head  end  diagrams  from  the  Ball 
engine  are  shown.  The  two  sets  of  diagrams  are  well  adapted 
for  comparison,  because  both  engines  are  of  the  single-valve  type, 
with  the  valve  moved  by  one  eccentric. 

The  points  to  be  noted  are,  first,  that  the  points  of  cut-off  are 
the  same,  namely  at  about  f  stroke,  in  all  the  throttling  cards, 
and  second,  that  the  power  of  the  engine  is  increased  by  the  action 
of  the  governor  in  opening  a  throttle  valve  wider,  allowing  steam 
to  enter  the  cylinder  at  higher  pressure. 

It  was  stated  at  the  outset  that  automatic  regulation  is  the 
most  approved  method  for  regulating  the  speed  of  steam  engines 
at  the  present  time.  It  is  generally  believed  and  it  is  probably 
true,  that  automatic  engines  give  better  economy  than  throttling 
engines  and  that  they  regulate  a  little  more  closely.  It  will 
readily  be  seen  that  when  the  governor  of  the  automatic  engine 


378  HANDBOOK    OX    ENGINEERING. 

changes  position,  it  measures  out  just  the  quantity  of  steam  that 
will  be  required  t'o  keep  the  engine  within  the  speed  limits  during 
the  following  stroke.  The  effect  of  this  regulation,  moreover,  is 
felt  at  one  point  in  the  stroke  only  —  the  point  of  cut-off  —  so  that 
any  change  in  the  governor  up  to  the  time  when  the  piston  nears 
the  point  of  cut-off  will  produce  an  immediate  change  in  the 
quantity  of  steam  admitted.  In  the  throttling  engine,  on  the 
other  hand,  the  regulation  is  effected  during  the  whole  stroke  up  to 
the  point  of  cut-off,  and  the  full  effect  of  any  change  of  the  gov- 
ernor cannot  be  felt  until  the  next  stroke.  With  regard  to  the 
relative  economy  of  the  two  types,  it  should  be  kept  in  mind  that 
the  throttling  engine  is  generally  of  cheap  construction,  has  large 
clearance,  a  single,  unbalanced  slide-valve  that  does  duty  for  both 
entering  and  exhaust  steam  and  aside  from  the  throttling  feature, 
is  inferior  to  the  average  automatic  engine.  It  is  reasonable  to 
suppose,  therefore,  that  at  least  a  part  of  the  large  steam  con- 
sumption generally  attributed  to  the  throttling  engine  is  due  to 
its  inferior  design  and  construction  and  not  to  its  method  of 
governing. 

For  example,  take  the  case  of  the  Ball  and  the  Dickson  engines, 
from  which  I  have  shown  cards.  They  both  have  a  single  slide- 
valve,  but  the  former  runs  at  higher  speed  than  the  latter  and  its 
valve  is  balanced,  so  that  for  these  reasons  it  would  be  expected 
to  be  a  little  more  economical.  We  should  not  expect,  however, 
that  a  test  would  show  any  decided  superiority  that  could  be 
attributed  to  the  method  of  governing.  If  we  were  to  compare 
the  average  throttling  engine  with  the  most  approved  type  of 
automatic  engine,  like  the  Corliss,  we  should  find  that  the  effi- 
ciency of  the  latter  was  much  higher.  The  gain,  however,  would 
be  due  to  a  large  extent  to  the  small  clearance  spaces,  separate 
steam  and  exhaust  valves,  and  other  important  features  of  the 
Corliss  engine,  rather  than  to  its  automatic  cut-off.  It  is  not 
the  purpose  to  discuss  here  why  these  features  give  improved 


HANDBOOK    ON    ENGINEERING.  379 

economy  over  the  single  valve,  but  simply  call  attention  to  the 
fact  that  they  exert  an  important  influence.  The  exact  influence 
which  the  throttling  or  automatic  features  exert  apart  from  the 
general  constructive  features  of  the  engine  is  hard  to  determine. 
It  is  known  that  high-pressure  steam  is  more  economical  to  use 
than  low  pressure  steam  and  the  automatic  engine,  which  pre- 
serves nearly  the  boiler  pressure  up  to  the  point  of  cut-off,  gains 
on  this  account.  On  the  other  hand,  it  is  known  that  the  most 
economical  point  of  cut-off  for  a  non-condensing  engine  is  about 
one-third  stroke,  and  when  it  becomes  very  much  less  than  this 
there  is  a  serious  drop  in  the  economy.  A  very  short  cut-off 
with  high-pressure  steam  produces  so  great  a  variation  in  the 
temperature  during  one  stroke  of  the  piston  that  the  cylinder 
condensation  becomes  excessive.  For  very  light  loads,  therefore, 
it  would  be  better  to  throttle  the  steam  than  to  shorten  the  cut-off. 
It  is  necessary  for  all  engines  to  have  a  reserve  of  power  and 
hence  the  cut-off  of  throttling  engines  must  come  late  in  the 
stroke.  If  it  were  early  in  the  stroke,  there  would  not  be  enough 
reserve  power  with  the  reduction  in  the  pressure  of  the  steam  that 
is  necessary  with  this  type.  The  late  cut-off  produces  poor 
economy  when  the  load  is  heavy,  because  there  will  then  be  a 
high  terminal  pressure,  and  a  large  amount  of  heat,  corresponding 
to  this  pressure,  will  be  thrown  away.  A  throttling  engine  there- 
fore, may  be  expected  to  do  better  at  light  loads  than  at  heavy 
ones,  and  in  fact,  may  do  a  little  better  at  light  loads  than  the 
automatic  engine.  If  a  throttling  engine  could  be  run  so  as  not 
to  vary  much  from  its  most  economical  load,  and  could  be  de- 
signed to  have  the  good  features  of  the  best  automatic  engines, 
with  the  cut-off  at  an  earlier  period  in  the  stroke,  it  would  prob- 
ably be  nearly  or  quite  as  well  as  the  automatic  engine.  Under 
the  conditions  that  they  have  to  run,  however,  the  automatic  engine 
will  keep  the  lead,  although,  as  explained  above,  its  superiority 
is  not  due  entirely  to  the  automatic  feature. 


380  HANDBOOK  OF  P^NGINEERING. 


CHAPTER     XV. 

Engineers  over  the  country  have  been  discussing  whether  or 
not  more  steam  is  used  when  an  engine  is  made  to  run  faster  without 
changing  either  the  cut-off  or  the  back  pressure.  Some,  strange  as 
it  may  seem,  have  actually  held  to  the  opinion  that,  since  the  cut- 
off is  not  changed,  no  more  steam  is  used,  and  hence,  if  it  were 
possible  to  make  an  engine  run  faster  without  changing  the  cut-off, 
it  would  be  doing  more  work  than  before  without  any  increase  in 
the  consumption  of  steam.  Of  course,  this  is  wrong.  The  speed 
of  an  engine,  almost  any  engine,  may  easily  be  increased  without 
changing  the  cut-off,  and  when  this  is  done,  the  engine  will  do 
more  work  and  will  use  more  steam.  It  is  utterly  impossible  to 
get  something  for  nothing  out  of  a  steam-engine,  or  out  of  any 
engine  or  appliance.  The  only  way  in  which  a  steam-engine  can 
be  made  to  do  more  work  without  using  more  steam  is  to  increase 
its  efficiency.  And  when  everything  else  is  kept  the  same  and  the 
speed  only  of  an  engine  increased,  the  efficiency  is  very  slightly 
increased.  The  condensation  is  decreased  with  an  increase  of 
speed,  but  the  decrease  would  be  so  slight  for  most  cases  that  it 
would  hardly  be  worth  considering.  When  an  engine  is  cutting 
off  at  a  certain  part  of  the  stroke,  it  uses  at  every  stroke  a  cer- 
tain weight  of  steam  which  depends  upon  the  initial  pressure  of 
the  steam,  clearance  volume  of  the  engine  and  the  point  of  cut- 
off. If  the  engine  makes  400  strokes  per  minute  (200  revolu- 
tions, if  a  double  acting  engine)  the  weight  of  steam  used  will  be 


HANDBOOK    ON    ENGINEERING.  381 

400  times  the  weight  used  in  one  stroke ;  but  if  the  engine  be 
made  to  make  500  strokes  per  minute,  the  weight  of  steam  used 
per  minute  will  be,  neglecting  the  small  difference  in  condensa- 
tion, 500  times  the  weight  used  in  one  stroke. 

HOW  TO  INCREASE  THE  SPEED,  OR  INCREASE  THE  POWER 
OF  A  CORLISS  ENGINE. 

There  are  three  ways  in  which  this  can  be  done.  Take,  for 
example,  a  24"x48"  simple  Corliss  engine  making  70  revolu- 
tions per  minute,  the  boiler  gauge  pressure  80  Ibs.  per  square 
inch,  one-quarter  cut-off,  or  cut-off  12  inches  from  the  beginning 
of  the  stroke  ;  the  mean  effective  pressure,  say  about  42  Ibs.  per 
sq.  in.,  the  governor  pulley  on  the  main  shaft  10  inches  in  diam- 
eter, the  pulley  on  the  governor  shaft  7  in.  in  diameter,  and  the 
friction  of  engine,  cylinder  clearance,  condensation,  etc.,  left 
entirely  out  of  the  question.  It  is  desired  to  increase  the  speed 
of  this  engine  to  80  revolutions  per  minute,  and  in  this  manner 
increase  its  horse-power. 

First  method*  —  Regardless  of  piston  rod,  the  area  of  the  pis- 
ton is  452.4  square  inches,  nearly.  The  piston  speed  of  this 
engine  is  560  feet  per  minute,  and  its  horse-power  322,  nearly. 

452.4x42x560 

Thus:   -  ~  =322.     So  that  the  horse-power  of  this 

ooUUU 

engine  at  70  revolutions  per  minute  is  322,  nearly,  and  this  is 
what  the  manufacturer's  catalogue  gives.  Now,  in  order  to  get 
80  revolutions  per  minute,  take  the  7-iuch  pulley  off  the  governor 
shaft,  and  put  in  its  place  an  8-inch  pulley.  Thus :  70 :  80 :  : 
7:8.  Then,  the  governor  balls  will  revolve  in  the  same  relative 
plane  that  they  did  before,  and  the  cut-off  will  remain  the  same ; 
that  is,  at  one-quarter,  or  12  in.  of  the  stroke.  Thus,  7:  10:: 
70  :  100.  And  8  :  10  :  :  80  :  100.  So  the  governor  balls  make  100 
revolutions  per  minute,  both  before  and  after  making  the  change. 


382  HANDBOOK    ON    ENGINEEKING. 

Now,  with  the  engine  speeded  up  to  80  revolutions  per  minute, 
we  get  46  more  horse-power.     Thus  :    Piston  speed  equals  640 

452.4x42x640 
feet    per   minute.     Then,       —       ?    --  ==  ^^     horse-power, 


nearly.     And  368  minus  322  =46.     Now,  it  would  appear  that 
we  are  getting  46  horse-power  more  for  nothing,  but  such  is  not 

452.  4x  12x2x70 
the  case.     For,    -         —        —       ~  =  439.8  +  ,    or    nearly     440 


cubic  ft.   of   steam   per   minute,   at  80   Ibs.    boiler  pressure,  are 

452.  4  x  12x2x80 
required  to  develop  322  horse-power.     And,    - 


=  502.6  +  or  nearly  503  cubic  ft.  of  steam  per  minute,  at  80 
Ibs.  boiler  pressure,  are  required  to  develop  368  horse-power. 
Then,  503  minus  440  =  63  cubic  feet  more  of  steam  at  80  Ibs. 
boiler  pressure,  which  means  more  water  evaporated  per  minute 
and  more  coal  burned  per  hour. 

Second  method*  —  Retain  the  same  engine  speed  and  the  same 
cut-off,  but  increase  the  boiler  pressure  from  80  to  90  Ibs.  Then 
80  :  90  :  :  42  :  47  +  ,  call  it  48  Ibs.  mean  effective  pressure. 

452.4x48x560 
Then,          —  ssooo  --  =  368    horse-power,   nearly,  the  same  as 

before,  and  as  given  in  the  manufacturer's  catalogue.  We  are 
now  using  440  cubic  feet  of  steam  per  minute  at  90  Ibs.  pressure, 
with  an  increase  of  6  Ibs.  M.  E.  P.  ;  consequently,  more  coal  per 
hour  must  be  burned. 

Third  method*  —  Retain  the  same  boiler  pressure,  that  is  80 
Ibs.,  and  weight  the  governor  so  as  to  make  the  balls  revolve  in  a 
lower  plane  in  order  to  give  a  later  cut-off  .  Thus,  322:  368:: 
i  :  |-.  That  is,  the  cut-off  must  take  place  at  about  -|  of  the 
stroke  instead  of  at  J.  Then,  J  :  f  :  :  42  :  48.  That  is  the 
M.  E.  P.  will  be  48  Ibs.  per  square  inch  with  a  cut-off  at  f  of  the 

452.  4  x  48  x  560 
stroke,   Then,  -        33000  —  ~~  =  368  horse-power,  the  same  as 


HANDBOOK    ON    ENGINEERING.  383 

I >f lore.  But,  -jj  of  48  =  1.')^,  or  13.71  inches  nearly,  so  that, 
instead  of  catting  off  at  12  inches  with  80  Ibs.  boiler  pressure, 
we  are  cutting  off  at  13.71  inches  and  using  63  cubic  feet  more 

452. 4  x  13,71x  2  x  70 

steam  per  minute.     Thus,  —  —  =  503,    nearly. 

1728 

And,  503  minus  440  =63,  that  is,  we  must  use  63  cubic  feet 
more  of  steam  per  minute  at  80  Ibs.  boiler  pressure,  in  order  to 
get  46  more  horse-power,  which  means  the  evaporation  of  more 
water  per  minute,  and  the  burning  of  more  coal  per  hour. 


HOW    TO    INCREASE    THE    HORSE=POWER    OF    AN    ENGINE 
HAVING  A  THROTTLING  GOVERNOR. 

There  are  three  ways  in  which  this  can  be  done,  also.  We 
will  take,  for  example,  a  plain  slide-valve  engine  10  x  16  inches, 
making  150  re  volutions  per  minute,  with  T9^  cut-off,  and  M.  E.  P. 
say  31|-  Ibs.  per  square  inch,  with  a  boiler  pressure  of  60  Ibs. 
by  gauge.  The  governor  pulley  on  the  main  shaft  6  inches 
in  diameter,  and  the  pulley  on  the  governor  shaft  4  inches 
in  diameter.  The  horse-power  of  this  engine  is  about  30. 

Thus,   -         -  =  2f  ft.,  and  150  x  2|  =  400  ft.,  the  piston  speed. 
1 2i 

10  x  10  x  .7854  x  31.5  x  400 

Then,  : —  30  horse-power,  nearlv. 

33000 

It  is  now  desired  to  run  the  engine  at  180  revolutions  per 
minute  in  order  to  develop  6  horse-power  more.  In  order  to 
obtain  these  results,  the  governor  pulley  must  be  enlarged,  so  as 
to  make  the  governor  balls  revolve  in  the  same  plane  at  180  revo- 
lutions per  minute,  that  they  now  do  at  150  revolutions.  Thus, 
4:6::  150:  225,  that  is,  the  governor  balls  are  now  making 
225  revolutions  per  minute.  And  150:180::4:4.8.  Con- 
sequently, the  governor  pulley  must  be  increased  to  4.8  inches  in 


384  HANDBOOK    ON    ENGINEERING. 

diameter.  Then,  4.8  :  6  :  :  180  :  225,  that  is,  the  governor  balls, 
after  the  change,  making  the  same  number  of  revolutions  as 
before.  At  180  revolutions  per  minute,  the  piston  speed  is  480 

feet    per    minute.     Thus,-   fJL  =  2f  .     And,    180x2f  =  480. 

Then,   78'54  x  31'5  x  48°  =  36  horse-power,  nearly.      It    might 
33000 

seem  from  the  above  that  we  are  getting  6  horse-power  more  for 
nothing  ;  but  such  is  not  the  case.  For,  cutting  off  at  T9¥  is 
equivalent  to  cutting  off  at  9  inches  of  the  stroke. 

™          78.54x9x2x150 

Then,   _  _=  123  cubic  ft.,  nearly. 

1728 

78.54x9x2x180 


1728 

147  minus  123  =  24.  So  that  for  6  horse-power  more,  we  are 
using  24  cubic  feet  more  of  steam  per  minute,  at  31.5  Ibs.  M.  E.  P., 
which  means  more  water  evaporated  per  minute  and  more  coal 
burned  per  hour. 

If  the  boiler  pressure  may  be  safely  increased,  we  can  get  6 
horse-power  more  out  of  the  engine  without  increasing  its  speed, 
by  running  the  boiler  pressure  up  to  75  Ibs.  by  gauge.  Thus  75 
Ibs.  boiler  pressure  would  give  about  37.8  Ibs.  M.  E.  P.  with  T9F 

cut-off:     Then,    ?8.54  x  37.8  x  400  =  86  ho         Qwer  nearly. 

33000 

In  this  case  no  change  should  be  made  in  the  governor,  nor  in 
the  speed  of  the  engine.  We  can  also  get  6  horse-power  more 
out  of  this  engine  by  cutting  off  later,  say  at  f  ,  in  order  to  get 
37.8  Ibs.  M.  E.  P.  But  a  later  cut-off  is  not  desirable,  because 
it  is  not  economical  of  steam,  and  besides,  it  would  require  a  new 
valve,  new  eccentric,  or  a  change  in  the  length  of  a  rocker  arm,  if 
not  a  change  of  the  valve-  seat,  because  the  travel  of  the  valve 
would  have  to  be  increased. 


HANDBOOK    OX    ENGINEERING. 


385 


HOW    TO    INCREASE   THE   HORSE=POWER    OF     AN     ENGINE 
HAVING  A  SHAFT  GOVERNOR. 

Suppose  it  is  desired  to  increase  the  speed  of  the  engine  from  250 
to  275  revolutions  per  minute,  cutting  off  at  i  stroke.  In  this 
case  the  governor  springs  should  be  so  adjusted  that  the  throw  of 
the  eccentric  will  be  the  same  at  275  revolutions  that  it  was  at  250 
revolutions.  This  will  require  an  increased  consumption  of  steam 
per  minute  at  the  same  initial  cylinder  pressure  as  before  making 
the  change,  consequently  more  fuel  will  be  required.  If  the  speed 
of  the  engine  is  not  to  be  changed,  an  increase  of  the  horse-power 
may  be  obtained  by  increasing  the  initial  cylinder  pressure,  if  the 
condition  of  the  boiler  will  so  permit.  Or,  the  initial  cylinder 
pressure  may  remain  unchanged  and  the  governor  springs  and 
levers  so  adjusted  as  to  give  a  later  cut-off,  say  at  |  or  -fs  of  the 
stroke,  or  whatever  may  be  required  to  offset  the  increased  per- 
manent load,  the  speed  of  the  engine  remaining  unchanged.  Any 
one  of  the  changes  above  described  would  necessitate  an  increased 
consumption  of  fuel. 

HOW  TO  LINE  THE  ENGINE  WITH    A    SHAFT  PLACED    AT  A 
HIGHER  OR  A   LOWER   LEVEL. 

We  will  suppose  the  latter  shaft  not  yet  in  place,  but  to  be 
represented  by  a  line  tightly  drawn.  From  two  points  as  far 
apart  as  practicable,  drop  plumb  lines  nearly,  but  not  quite, 
touching  this  line.  Then  by  these  strain  another  line  parallel 
with  the  first,  and  at  the  same  level  as  the  center  line  of 
tli*1  engine,  and  at  right  angles  with  this  stretch  another  represent- 
ing this  center  line,  and  extend  both  each  way  to  permanent  walls 
on  which  their  terminations,  when  finally  located,  should  be  care- 
fully marked,  so  they  can  at  any  time  be  reset.  The  problem  is 
to  get  the  latter  line  exactly  at  right  angles  with  the  former. 
Everything  depends  upon  the  accuracy  with  which  this  right 

25 


386 


HANDBOOK    ON    ENGINEERING. 


angle  is  determined.  It  is  done  by  the  method  of  right-angled 
triangles.  There  are  two  ways  of  applying  this  method.  In  the 
first,  one  end  of  a  measuring  line  is  attached  to  some  point  of 
line  No.  1,  and  its  other  end  is  taken  successively  to  points  on 
line  No.  2  on  opposite  sides  of  the  intersection,  as  illustrated  in 
the  following  figure,  in  which  A  B  is  a  portion  of  line  No.  1,  and 
C  I)  of  line  No.  2,  the  direction  of  which  is  to  be  determined. 
B  F  and  B  G  are  the  same  measuring  line  fixed  at  JB,  and  applied 
to  the  line  C  I)  successively  at  the  points  F  and  (*.  The  dis- 


tances B  Fand  B  G  being,  therefore,  the  same,  when  E  F  is 
equal  to  E  G,  the  lines  A  B  and  C  D  are  at  right  angles  with  each 
other.  In  the  second,  application  is  made  of  the  law  that  the  square 
of  the  hypothenuse  of  a  right-angle  triangle  is  equal  to  the  sum 
of  the  squares  of  the  other  two  sides.  Thus  32  -f-  42  =  52.  So  if 
the  above  figure  E  B  =  4,  E  F  =  3,  and  B  F=  5,  the  angle  at 
E  is  a  right-angle.  Any  uru't  of  measure  may  be  used,  a  foot  is 
generally  the  convenient  one ;  so  any  multiple  of  these  numbers 
may  be  taken;  as,  for  example,  6,  8  and  10.  Respecting  the 
comparative  advantages  of  these  two  ways,  the  situation  will  often 
determine  which  is  to  be  preferred.  In  the  former,  the  diagonal 


HANDBOOK    ON    ENGINEERING.  387 

being  the  same  line,  fixed  at  B  and  brought  successively  to  the 
points  F  and  6r,  its  length  is  immaterial,  though  generally  the 
longer  the  better ;  and  the  only  point  to  be  determined  is  the 
equality  of  E  F  and  E  G,  which  may  be  compared  with  each 
other  by  marks*  on  a  rod.  In  the  latter,  the  proportionate 
lengths,  3,  4  and  5.  or  their  multiples,  must  be  exactly  measured. 
It  is  better  adapted  to  places  where  a  floor  is  laid  and  the  meas- 
urements can  be  transferred  by  trammels.  The  result  should  be 
verified  by  repeating  the  operation  on  the  opposite  side  of  the 
intersection  at  E,  and  when  so  verified  we  have,  in  fact,  the  first 
process,  without  the  additional  and  unnecessary  trouble  of  deter- 
mining the  relative  lengths  of  the  lines.  Care  should  be  taken 
when  a  measuring  line  is  used,  to  avoid  errors  from  its  elasticity . 
On  this  account,  a  rod  is  often  employed.  Points  on  the  lines 
are  best  marked  by  tying  on  a  white  thread. 

HOW  TO  LINE  THE  ENGINE  WITH  A  SHAFT  TO   WHICH  IT  IS 
TO  BE  COUPLED  DIRECT. 

In  this  case,  it  is  supposed  that  the  engine  bed  and  the  bear- 
ings for  the  shaft  are  already  approximately  in  position.  They 
are  leveled  by  a  parallel  straight  edge  and  a  spirit  level.  To  line 
then)  horizontally,  a  line  must  be  run  through  the  whole  series  of 
hearings  and  continued  to  a  permanent  wall  at  each  end,  and  its 
terminating  points,  when  determined,  carefully  marked,  as  already 
directed.  A  piece  of  wood  is  tightly  set  in  each  end  of  each 
bearing  and  the  surfaces  of  these  are  painted  white  or  chalked. 
Then  the  middle  of  each  piece  being  found  by  the  compasses,  two 
fine  lines  are  drawn  across  it,  equally  distant  from  the  middle,  and 
having  between  them  a  space  a  little  wider  than  the  thickness  of 
the  line.  This  being  then  strained,  nearly  touching  those  blocks; 
or,  if  long,  having  its  sag  supported  by  them,  the  two  marks  on 
each  block  must  be  seen,  one  on  each  side  of  the  line,  with  the 
line  of  white  between. 


388  HANDBOOK    ON    ENGINEERING. 

HOW  TO  SET  A  SLIDE  VALVE  IN  A  HURRY. 

Open  your  cylinder  cocks ;  then  open  the  throttle  slightly,  so 
as  to  admit  a  small  amount  of  steam  to  the  steam-chest.  Roll 
your  eccentric  forward  in  the  direction  the  engine  runs,  until 
steam  escapes  from  the  cylinder  cock  at  the  end  where  the  valve 
should  begin  to  open.  Now  screw  your  eccentric  fast  to  the 
shaft.  Roll  your  crank  tojthe  next  center  and  ascertain  if  steam 
escapes  at  the  same  point,  at  the  opposite  end  of  the  cylinder. 
If  so,  ring  your  bell  and  go  ahead.  You  are  all  right  and  can  run 
until  an  opportunity  occurs  to  you  to  open  your  steam-chest  and 
examine  your  valve. 

DO  YOU  DO  THESE  THINGS? 

A  writer  in  a  contemporary  asks  and  answers  the  following 
pertinent  questions :  - 

Do  you  take  a  squirt-can  in  one  hand  and  project  a  stream  of 
oil  as  far  as  you  can  throw  it,  in  order  to  save  going  to  the  oil 
hole  itself  ? 

If  you  do,  don't  do  it  any  more  ;  willful  waste  is  downright 
robbery. 

Do  you  use  an  oil  can  at  all  for  oiling,  except  on  emergency,  or 
for  the  moment  ? 

If  you  do,  don't  do  it  any  more,  for  much  better  lubrications 
can  be  had  by  automatic  apparatus. 

Do  you  keep  an  old  tin  coffee  pot  full  of  suet  on  the  steam- 
chest,  and  every  tiine  you  have  nothing  else  to  do,  pour  a  dipper- 
ful  into  the  steam-chest? 

If  you  do,  stop  it  and  get  a  sight-feed  cup,  which  will  save 
you  the  labor  of  slushing  the  cylinder  and  save  the  cylinder  and 
valve-seats,  the  piston  and  follower,  and  all  other  places  touched 
by  the  grease. 


HANDBOOK    ON     KN<;  INHERING.  389 

Do  you  feed  the  boiler  until  the  water  is  out  of  sight  in  the 
glass,  then  shut  off  the  feed,  put  in  a  big  fire  and  sit  down  in 
a  dark  corner  with  a  four-horse  brier  pipe  and  smoke,  until  you 
happen  to  think  that  maybe  the  water  is  low? 

If  you  do  these  things  you  should  notify  the  coroner  that  some 
day  his  services  will  be  needed,  but  it  is  better  to  cease  the  prac- 
tice mentioned  before  the  coroner  comes.  • 

Do  you  stop  leaks  about  the  boiler  as  fast  as  they  occur,  or  do 
you  wait  until  the  places  sound  like  a  snake's  den  before,  you  stir? 

If  you  do,  you  waste  heat, 'which  is  the  same  word  as  money, 
only  differently  spelled.  Every  jet  of  hot  water  leaking  from  a 
steam  boiler  is  just  so  much  money  thrown  away,  and  if  it  was 
your  money  you  would  be  bankrupt  in  a  short  time,  in  some 
boiler  rooms. 

Do  you  take  a  screw  wrench  and  yank  away  at  a  bolt  or  nut 
under  steam  pressure? 

If  you  do,  there  will  come  a  time,  sooner  or  later,  when  you 
will  do  so  once  too  often,  and  either  kill  yourself  or  some  one  else. 
Bolts  and  nuts  are  liable  to  strip  or  break  if  tampered  with  under 
pressure,  and  they  never  tell  any  one  beforehand  when  they  are 
going  to  do  it. 

Do  you  attempt  to  stop  pounding  in  the  engine  by  laying  for 
the  crank-pin  as  it  comes  round,  and  trying  to  hit  the  key  once  in 
a  while? 

If  you  do,  ask  the  strap  and  neck  of  the  connecting-rod  how 
he  likes  it,  when  you  don't  hit  the  key  and  do  hit  the  oil  cup? 

Do  you  pack  the  piston  by  taking  it  out  of  the  cylinder,  lay- 
ing it  on  the  floor,  setting  out  the  rings,  and  then  when  the  piston 
will  not  go  into  the  cylinder,  try  to  batter  it  in  with  a  four-foot 
stick  of  cord  wood? 

If  you  dQ,  you  should  reform,  and  pack  the  piston  in  the 
cylinder  where  it  belongs,  being  sure  to  get  it  central  by  meas- 
uring from  the  lathe  center  in  the  end  of  the  piston  rod. 


390 


HANDBOOK    ON    ENGINEERING. 


Do  you  put  a  new  turn  of  packing  on  top  of  the  old,  lisird- 
burned  stuff  when  the  piston  rod  leaks  steam  ? 

If  you  do,  you  will  have  a  scored  piston  rod  and  broken  gland 
bolts  some  day.  Packing  under  heat  and  pressure  gets  so  hard 
that  it  cuts  like  a  file  when  left  in  the  stuffing  box,  and  as  one 
begins  to  leak  all  the  old  stuff  should  be  pulled  out  and  new  put 
in  its  place. 


Fig.  1. 


Fig.  2. 


THK    TRAVEL    OF    A    SIDE    VALVE. 

4 

The  travel  of  a  slide  valve  is  found  as  follows :  The  maximum 
port  opening  at  the  head  end,  plus  the  maximum  port  opening  at 
the  crank  end,  plus  the  lap  at  the  head  end,  plus  the  lap  at  the 
crank  end.  Therefore —  If"  -f-  If"  -f-  £"  +  f"  =4J",  the  re- 
quired travel:  of  valve.  Incidentally,  it  may  be  well  to  mention 
that  the  travel  of  a  valve  may  also  be  obtained  from  the  eccentric, 
by  subtracting  the  thin  part  of  the  eccentric  from  the  thick 
part  as  per  Fig.  1,  or  again,  by  taking  twice  the  distance  between 
the  center  of  rotation  and  center  of  the  eccentric.  This  distance 
on  the  eccentric  is  the  end  valve  travel,  and  is  termed  the  "  throw  " 
of  the  eccentric.  In  the  above  question,  the  travel  may  also  be 


HANDBOOK    ON    ENGINEERING. 


391 


found  by  the  aid  of  the  diagram,  Fig.  2,  which  is  explained  as 
follows:  From  the  center  A,  with  a  radius  of  J  inch  (lap), 
describe  a  circle  B  C  D.  From  any  point,  in  the  circumference, 
say  12,  lay  off  the  distance  B  E  equal  to  the  maximum  port  open- 
ing. If"  ;  from  the  center  A,  with  a  radius  A  E,  describe  the 
circle  E  F  G;  the  diameter  of  the  circle  .E  F  G  is  equal  to  the 
travel  of  the  valve,  which  is  4J".  Let  the  readers  try  this  with 
another  set  of  figures,  to  prove  the  correctness  of  the  diagram. 

LOSS  OF  HEAT  FROM  UNCOVERED   STEAM  PIPES. 

The  following  table  shows  the  loss  of  heat  through  naked  steam 
pipes,  wrought  iron,  of  standard  sizes.  The  best  covering  for  a 
steam  pipe  is  hair  felt  from  one  to  two  inches  thick,  depending  on 
the  diameter  of  the  pipe,  say  one  inch  thick  for  pipe  from  1  to  4 
inches  in  diameter,  and  two  inches  or  more  for  larger  pipes. 
Such  covering  will  save  at  least  96  per  cent.  Cheaper  coverings 
will  save  from  75  to  90  per  cent.  The  chief  value  of  the  table  is 
as  an  aid  in  estimating  the  saving  that  can  be  made  by  covering 
the  pipe.  The  money  loss  by  naked  pipe  being  known,  the  sav- 
ing can  be  estimated  and  the  cost  of  the  covering  will  decide  its 
value  as  an  investment. 

TABLE  OF  MONEY  LOSS  FROM  100  FEET  OF  NAKED  STEAM  PIPE,  FOR 
ONE  YEAR  OF  3000  WORKING  HOURS. 


—  «  fl 

STEAM  PRESSURES. 

§|«» 

50 

60 

70 

80 

90 

100 

fc^  0.5 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

1 

$13.15 

$13.70 

$14.20 

$14.66 

$15.08 

$15.47 

U 

16.58 

17.29 

17.92 

18.49 

19.02 

19.51 

if 

18.98 

19.78 

20.51 

21.17 

21.77 

22.33 

2 

23.72 

24.73 

25.63 

26.45 

'   27.21 

27.91 

2JL 

28.72 

29.94 

31.03 

32.03 

32.94 

33.79 

38 

34.97 

36.45 

37.78 

38.99 

40.10 

41.14 

4 

44.96 

46.86 

48.57 

50.13 

51.56 

,02.89 

5 

55.57 

57.92 

60.04 

61.96 

63.73 

65.38 

6 

66.27 

69.08             71.60 

73.89 

76.01 

77.96 

392  HANDBOOK    ON    ENGINEERING. 


RULES    AND    PROBLEMS    APPERTAINING    TO    THE    STEAM 

ENGINE. 

To  find  the  H.  P.  of  a  simple  non-condensing  engine :  — 

Rule* — •  Multiply  the  net  area  of  the  piston  in  square  inches, 
by  the  mean  effective  pressure  in  pounds  per  square  inch,  and  by 
the  velocity  of  the  piston  in  feet  per  minute,  and  divide  the  last 
product  by  33,000.  The  quotient  will  be  the  gross  H.  P.  Sub- 
tract from  this  from  ten  to  twenty  per  cent  for  friction  in  the 
engine  itself,  and  the  remainder  will  be  the  delivered  H.  P. 

Example*  —  The  area  of  the  piston  is  500  sqr.  ins.  Half  the 
area  of  the  piston-rod  is  5  sqr.  ins.  The  M.  E.  P.  is  50  Ibs. 
per  sqr.  in.  The  stroke  is  3  feet,  and  the  revolutions  per  minute 
125.  The  friction  is  10  per  cent.  What  is  the  delivered  H.  P. 
of  the  engine?  Ans.  506.25  H.  P. 

Operation* —  3  ft.  X  2  =  6  ft.  twice  the  stroke. 

Then,  500  —  5  =495  sqr,  ins.  net  area  of  piston. 

And,  125  X  6  =  750  ft.  the  piston  speed  per  minute. 

^495X50X750 
33,000 

Then,  562.5  X  .90  =  506.25.     The  delivered  H.  P. 

For  a  condensing  engine:  — Add  the  vacuum  to  the  M.  E.  P. 
and  proceed  as  above. 

The  M.  E.  P.  is  the  average  pressure  in  the  cylinder,  less  the 
back  pressure. 

To  find  the  H.  P.  of  a  compound  noncondensing  engine :  — 

The  usual  method  of  calculating  the  H.  P.  of  a  multiple  cyl- 
inder engine  is  to  assume  that  all  the  work  is  done  in  the  low 
pressure  cylinder  alone,  and  that  such  a  M.  E.  P.  is  obtained  in 
that  cylinder  as  will  give  the  same  H.  P.  as  is  given  by  the  whole 
engine. 

Rule*  —  Find  the  ratio  of  areas  of  the  high  and  low  pressure 
cylinders, —  when  of  the  same  stroke,  as  they  usually  are, —  and 


HANDBOOK    ON    ENGINEERINO.  393 

multiply  it  by  the  number  of  expansions  in  the  high  pressure 
cylinder,  for  the  total  number  of  expansions  in  both  cylinders. 
Find  -the  hyperbolic  logarithm  corresponding  to  this  result  and 
add  1  to  it,  and  divide  the  sum  by  the  total  number  of  expan- 
sions. Multiply  this  result  by  the  absolute  steam  pressure,  and 
subtract  the  back  pressure.  Subtract  again  the  loss  in  pressure 
between  cylinders,  and  the  remainder  will  be  the  M.  E.  P.  Then 
multiply  the  net  area  of  the  low  pressure  cylinder  by  this  M.  E.  P. 
and  by  the  piston  speed  in  feet  per  minute  and  divide  by  33,000. 
Deduct  the  friction  in  the  engine  itself  and  the  remainder  will  be 
the  delivered  H.  P. 

Example.  —  Given  a  tandem  compound  engine  with  cylinders 
20"  and  32"  diameter,  and  4  feet  stroke,  making  75  revolutions 
per  minute,  boiler  gauge  pressure  125  Ibs.  per  sqr.  in.,  J  cut-off 
in  high  pressure  cylinder,  back  pressure  15J  Ibs.  per  sqr.  in., 
drop  in  pressure  between  cylinders  15  per  cent,  and  friction  in 
engine  10  per  cent.  What  is  the  H.  P.  delivered  of  this  engine? 
Ans.  338.4  H.  P. 

Operation*  —  Neglecting  the  areas  of  the  piston  rods,  we 
have :  - 

20  X  20  X  .7854  =  314.16  sqr.  ins.  area  of  high  pressure 
cylinder. 

And,  32  X  32  X  .7854  =  804,2  sqr.  ins.  area  of  low  pressure 
cylinder.  * 

Then,  804.2  -i-  314.16  =  2.56  =  the  ratio  between  cylinders. 

And,  2.56  X  4  =  10.24  =  the  total  number  of  expansions. 
The  hyperbolic  logarithm  of  10.24  =  2.328.  (Seetableonp.  397.) 

And,  1  +  2.328  =  3.328. 

Then,  3.328  4-  10.24  =  .325. 

Also,  125  -f-  15  —  140  Ibs.,  the  absolute  pressure. 

And,  .325  X  140  =45.5  Ibs.,  forward  pressure. 

And,  45.5  —  15.25  =  30.25  Ibs.,  the  M.  E.  P. 


394  HANDBOOK    OX    ENGINEERING. 

And,     30.25  X  .85  =  25.7    Ibs. -^  the    M.    E.    P.    less    the 
"  drop." 

804.2  X  25.7  X  8  X  75 

Then,    -  —  =376  H.  P.  nearly. 

33,000 

And,  376  X  .90  =  338.4  H.  P.  delivered. 

For  a  compound  condensing  engine,  proceed  as  above,  except 
that  the  condenser  pressure,  due  to  impaired  vacuum,  only  should 
be  subtracted  from  the  forward  pressure. 

To  find  the  linear  expansion  of  a  wrought-iron  pipe  or  bar :  — 

Rule*  — Multiply  the  length  of  the  pipe  or  bar  in  inches  by 
the  increase  in  temperature,  and  by  the  constant  number  .0007, 
and  divide  the  last  product  by  100. 

Example* — Given  a  6  inch  wrought-iron  pipe  75  feet  long. 
Steam  pressure  150  Ibs.  by  gauge.  Temperature  of  pipe  when 
put  up  60  degs.  Fah.  What  is  its  linear  expansion?  Ans. 
2  ins.  nearly. 

Operation.  —  The  diameter  of  the  pipe  cuts  no  figure. 

Then,  150  Ibs.  pressure  =  366  degs. 

And,  366  —  60  =  306  degs. 

Also,  75  X  12  =  900  inches  length  of  pipe. 

The,.   306   X900X  .0007  =1>9a78ineh- 

For  copper,  use  the  constant  number  .0009  ;  for  brass,  use 
.00107  ;  for  fire-bjick,  use  .0003,  and  proceed  as  above. 

To  find  the  proper  diameter  of  steam  pipe  for  an  engine :  - 

The  velocity  of  steam  flowing  to  an  engine  should  not  exceed 
6,000  feet  per  minute. 

Rule.  —  Multiply  the  area  of  the~piston  in  square  inches  by  the 
piston  speed  in  feet  per  minute,  and  divide  by  6,000  ;  and  divide 
again  by  .7854,  and  extract  the  square  root  for  the  diameter  of  the 
pipe  and  take  the  nearest  commercial  size. 

Example*— Given  a  20"  X  48"  Corliss  engine  making  72  revo- 
lutions per  minute.  What  should  be  the  diameter  of  its  steam 
pipe?  Ans.  6  inches. 


HANDBOOK   ON    ENGINEERING.  395 

Operation*—  20  X  20  X  .7854  r=314.16  sqr.  ins. 

And,  48"  X  2  X  72  =  576  ft.  the  piston  speed. 
12 

And.  314-16X576=  30.15. 
6,000 

Then,  =  6.1".    Take  6"  pipe. 


To  find  the  water  consumption  of  a  steam  engine  :  — 
The  most  reliable  method  for  determining  this,  is  to  make  an 
evaporation  test,  that  is,  to  measure  the  water  fed  to  the  boiler  in 
a  given  time  and  delivered  to  the  engine  in  the  form  of  steam. 
But  as  this  method  entails  considerable  trouble  and  expense,  it  is 
frequently  figured  from  indicator  diagrams.  This  plan,  however, 
does  not  insure  correct  results,  because  the  amount  of  water  ac- 
counted for  by  the  indicator  is  considerably  less  than  it  should  be 
owing  to  cylinder  condensation  and  leakage,  so  that  it  might  be 
possible  that  only  80  per  cent  of  the  water  passing  through  the 
cylinder  would  be  accounted  for  by  the  indicator.  But  the  cal- 
culation, used  in  connection  with  an  evaporation  test,  will  reveal 
the  extent  of  the  losses  caused  by  cylinder  condensation  and 
leakage,  by  deducting  the  amount  of  water  found  by  computation 
from  the  amount  of  water  fed  to  the  boiler  while  making  an 
evaporation  test. 

Rule.  —  Divide  the  constant  number  859,375  by  the  M.  E.  P. 
of  any  indicator  card,  and  divide  this  quotient  by  the  volume  of 
its  total  terminal  pressure,  the  result  will  be  the  theoretical  con- 
sumption in  pounds  of  water  per  horse  power  per  hour. 

The  constant  number  859,375  is  found  as  follows:  — 

Compute  the  size  of  an  engine  that  will  give  just  one  horse- 
power at  one  pound  M.  E.  P.  per  square  inch,  thus: 

Area  of  piston  equals  412.5  sqr.  inches. 

Stroke  equals  4  feet,  and  revolutions  per  minute  equal  10. 


396 


HANDBOOK    ON    ENGINEERING. 


Then,  the  piston  speed  is  (4  X  2  X  10)  80  feet  per  minute. 
412.5  X  1X80 

And'       -88^00- 

To  find  how  much  water  it  would  take  to  run  this  engine  one 
hour,  allowing  02 1  Ibs.  to  the  cubic  foot  of  water,  proceed  as 
follows :  — 

Twice  the  stroke  equals  90  .inches. 

Then,   -  equals  2 2. 9 10 GO  cubic  feet  for  one  revo- 

1728    . 

lution. 

And,  22.91600  X  10  equals  229.1000  cubic  feet  for  10  revolu- 
tions, or  for  one  minute. 

Then,  229.1000  X  60  X  02J  equals  859,375  Ibs.  of  water  used 
per  hour. 


T 


SCALE  40 

M.  E.  P. 
13  7.  6  LBS. 


Fig.  1  is  not  an  actual  indicator  card,  but  answers  to  illustrate 
the  rule. 

A  A  is  the  atmospheric  line,  and  from  A  to  A  is  the  whole 
stroke. 

VV  is  the  vacuum  line. 

Points  (a)  and  (?>)  are  equally  distant  from  the  vacuum  line. 
The  point  (a)  is  taken  at  or  very  near  the  point  of  release. 


HANDBOOK    ON    ENGINEERING. 


397 


Example. —  From  the  indicator  card  Fig.  1  compute  the  water 
consumption,  the  M.  E.  P.  being  37.6  Ibs.  per  square  inch,  the 
scale  of  spring  used  in  the  indicator  being  40,  the  distance  from 
point  (a)  to  point  (fr)  being  3.03  inches,  the  stroke  A  A  being 
3.45  inches,  and  the  pressure  at  point  («)  being  25  Ibs.  per  sqr. 
inch  absolute.  Ans.  20.14  Ibs. 

Operation*—  859,375  ~-  37.6  =  22,855.7. 

Now,  the  absolute  pressure  at  point  (//)  is  25  Ibs.,  and  steam 
tables  give  996  as  the  volume  of  steam  at  this  pressure,  that  is, 
steam  at  this  pressure  has  996  times  the  bulk  of  the  water  from 
which  it  was  generated. 

Then,  22,855.7  -f-  996  =  22.94  Ibs.  of  water.  But  as  the 
period  of  consumption  is  represented  by  (6)  (a),  AA  being  the 
whole  stroke,  the  following  correction  is  required :  The  distance 
from  point  (a)  to  point  (b)  is  3.03  ins.  Then,  22.94  X  3.03  = 
69.5080.  And  the  whole  stroke  or  length  of  line  AA  is. 3. 45 
ins. 

Then,  69.5080  -^-3.45  =  20.14*  Ibs.  of  water  per  indicated 
horse  power  per  hour. 

TABLE    OF    HYPERBOLIC    LOGARITHMS. 


NO. 

LOGARITHM. 

NO. 

LOGARITHM. 

NO. 

LOGARITHM. 

1.25 

.22314 

5. 

1.60943 

9.5 

2.25129 

1.0 

.40546 

5.25 

1.65822 

10. 

2.30258 

1.75 

.55961 

5.5 

1.70474 

10.24 

2.328 

2. 

.69314 

5.75 

1.74917 

11. 

2.39789 

2.25 

.81093 

6. 

1.79175 

12. 

2.48490 

2.5 

.91629 

6.25 

1.83258 

13. 

2.56494 

2.TS 

.01160 

6.5 

1,87180 

14. 

2.63905 

3. 

.09861 

6.75 

1.90954 

15. 

2.70805 

3.25 

.17865 

7. 

1.94591 

16. 

2.77258 

3.5 

.25276 

7.25 

1.98100 

17. 

2.83421 

3.75 

.32175 

7.5 

2.01490 

18. 

2.89037 

4. 

.38629 

7.75 

2.04769 

19. 

2.94443 

4.25 

.44691 

8. 

2.07944 

20. 

2.99573 

4.5 

.50507 

8.5 

2.14006 

21. 

3.04452 

4.75 

.55814 

9. 

2.19722 

22. 

3.09104 

398  JIANDHOOK    ON*    ENGINEERING. 

THE  STEAM  BOILER. 

CHAP  T  K  R     XVI. 
THE  FORCE  OF  STEAM  AND  WHERE  IT  COMES  FROH. 

If  water  he  heated  it  will  expand  somewhat,  and  will  finally 
burst  forth  into  vapor.  The  vapor  will  expand  enormously,  and 
naturally  occupy  more  space  than  the  water  from  which  it  is 
formed.  'A  cubic  inch  of  water  will  make  a  cubic  foot  of  steam  : 
that  is,  the  water  has  been  expanded  by  heat  to  seventeen  hundred 
times  its  original  bulk.  The  steam  is  very  elastic;  the  water  was 
not.  When  we  say  that  a  cubic  inch  of  water  will  form  a  cubic 
foot  of  steam,  we  mean  that  it  will  do  so  when  the  steam  is  allowed 
to  rise  naturally  from  the  water  without  any  confinement.  If  the 
steam  is  confined,  as  it  would  be  in  a  boiler,  it  could  not  expand, 
and  consequently  would  not.  If  the  steam  is  allowed  to  rise  into  the 
atmosphere  from  an  open  vessel,  the  pressure  of  the  steam  would  be 
precisely  the  same  as  the  pressure  of  the  atmosphere,  that  pressure 
being  about  fifteen  pounds  to  the  square  inch.  An  ordinary  steam 
gauge  only  takes  notice  of  the  pressure  above  the  atmospheric 
pressure.  When  the  hand  of  the  steam  gauge  stands  at  zero,  it 
indicates  that  there  is  no  pressure  above  the  ordinary  pressure  of 
the  atmosphere.  An  ordinary  steam  gauge  not  connected  with 
anything  has  the  atmosphere  acting  upon  it  in  both  directions,  the 
same  as  the  atmosphere  acts  upon  everything  when  it  can  reach 
both  sides.  If  the  air  be  pumped  out  of  the  steam  gauge,  the 
atmosphere  will  then  act  upon  one  side,  and  the  hand  will  move 
backward  until  it  stands  at  fifteen  points  less  than  nothing.  In 
this  condition  the  steam  gauge  indicates  the  absolute  zero  of 
pressure.  If  now  the  air  be  allowed  to  re-enter  where  it  was 
pumped  out,  it  will  begin  to  exert  its  pressure  upon  the  steam 


HANDBOOK    ON    ENGINEERING.  399 

gauge,  and  the  hand  will  move  forward ;  when  the  full  air 
pressure  is  on,  the  gauge  hand  will  stand  at  its  usual  zero. 
To  go  into  this  matter  in  order  that  it  may  be  understood 
that  the  real  pressure  of  steam  is  always  fifteen  pounds  greater 
than  ordinary  steam  gauges  indicate.  In  all  of  the  finer  cal- 
culations relating  to  the  action  of  steam,  its  total  pressure  must 
be  known,  and  this  total  pressure  is  to  be  counted  from  the 
absolute  zero.  The  real  pressure  of  steam  is  always  the  steam 
gauge  pressure,  plus  fifeeen  pounds.  When  a  steam  gauge  shows 
lifty  pounds,  the  steam  really  has  a  pressure  of  sixty-five  pounds. 
The  fifteen  pounds  of  this  pressure  is  nullified  by  the  atmospheric 
pressure,  and  the  steam  gauge  shows  us  our  useful  pressure.  As 
before  stated,  a  cubic  inch  of  water  will  make  a  cubic  foot  of 
steam  at  atmospheric  pressure;  that  is,  fifteen  pounds  to  the 
sq uare  inch,  abolute  pressure,  or  zero  by  the  steam  gauge.  If 
this  cubic  inch  of  water  was  made  into  steam  in  a  boiler  holding 
just  a  cubic  foot,  the  steam  gauge  would  show  zero.  If  the  boiler 
was  only  large  enough  to  hold  half  a  cubic  foot,  the  steam  would 
all  be  in  the  boiler,  and  being  confined  in  half  its  natural  space, 
it  would  have  double  pressure.  It  would  have  an  absolute  pres- 
sure of  thirty  pounds  to  the  square  inch,  and  the  steam  gauge 
would  indicate  fifteen  pounds.  If  this  steam  was  then  allowed  to 
pass  into  a  chamber  holding  a  cubic  foot,  the  steam  would  expand 
until  it  filled  the  chamber,  and  its  pressure  would  go  down  again 
to  fifteen  pounds  absolute.  N  In  short,  the  pressure  is  in  reverse 
proportion  to  the  amount  of  space  it  occupies.  The  pressure  of 
steam  may  be  doubled  by  compressing  the  steam  into 
one-half  its  former  volume,  and  so  on.  After  water  is 
turned  into  steam,  the  steam  may  be  made  hotter,  but 
it  is  not  very  much  expanded.  The  pressure  of  steam 
is  increased  by  forcing  more  steam  into  the  space  occupied. 
If  a  boiler  contains  steam  at  50  Ibs.  pressure,  we  may  increase 
the  pressure  by  adding  more  steam,  and  thus  compressing  all  the 


400  HANDBOOK    ON    ENGINEERING. 

steam  that  the  boiler  contains.  In  the  ordinary  operation  of  a 
steam  boiler,  the  fire  turns  the  water  into  steam  and  the  more 
steam  there  is  made  and  confined,  the  greater  the  pressure  will 
be.  If  the  steam  is  constantly  (lowing  out  of  the  boiler  into  an 
engine,  the  pressure  in  the  boiler  must  be  kept  up  by  continually 
making  new  steam  to  take  the  place  of  that  drawn  off.  If  we 
make  steam  as  fast  as  it  is  drawn  off,  and  no  faster,  the  pressure 
will  remain  the  same.  If  we  make  steam  faster  than  the  engine 
draws  it  off,  the  pressure  will  rise,  and  if  it  is  drawn  off  faster 
than  we  make  it,  the  pressure  will  go  down. 

The  pressure  of  the  steam  is  due  to  its  desire  to  expand  into  a 
larger  body,  and  it  acts  outwardly  in  every  direction  against 
everything  upon  which  it  presses.  If  we  crowd  GOO  cu.  ft.  of 
steam  in  a  boiler,  which  will  only  hold  100  cu.  ft.,  the  steam  will 
be  held  compressed  into  one-sixth  its  natural  bulk,  and  will  thus 
have  a  pressure  of  90  Ibs.,  and  the  steam  gauge  will  show  75  Ibs. 
If  a  hole  1  in.  square  be  cut  in  the  boiler,  and  a  weight  of  75  Ibs. 
be  laid  over  the  hole,  the  steam  will  just  lift  the  weight.  If  the 
atmospheric  pressure  could  be  removed  from  one  sq.  in.  of  the 
top  of  the  weight,  the  steam  would  then  be  capable  of  lifting  a 
90  Ib.  weight.  The  force  which  this  steam  will  exert  to  lift  a 
weight,  or  any  similar  thing  against  which  it  acts,  will  equal  the 
pressure  per  square  inch  multiplied  by  the  number  of  square 
inches  which  the  steam  acts  upon.  It  will  thus  be  readily  under- 
stood that  if  we  lead  a  pipe  from  the  boiler  and  lit  a  piston  in  the 
pipe,  the  steam  will  tend  to  force  this  piston  out  of  the  pipe. 

THE   ENERGY   STORED   IN  STEAM   BOILERS. 

A  steam  boiler  is  not  only  an  apparatus  by  means  of  which  the 
potential  energy  of  chemical  affinity  is  rendered  actual  and  avail- 
able, but  it  is  also  a  storage  reservoir,  or  a  magazine,  in  which  a 
quantity  of  such  energy  is  temporarily  held  ;  and  this  quantity, 


HANDBOOK    ONT    ENGINEERING.  MM 

enormous,  is  directly  proportional  to  UK;  weight  of  water 
and  of  steam  which  the  boiler  at  the  time  contain**.  The  energy 
of  gunpowder  is  somewhat  variable,  but  a  cubic  foot  of  heated 
water  under  a  pressure  of  GO  or  70  Ibs.  per  square  inch,  has  about 
the  same  energy  as  one  pound  of  gunpowder ;  at  a  low  red  heat, 
it  has  about  forty  times  this  amount  of  energy. 

The  letters  B.  T.  U.  are  the  initial  letters  of  the  words  British 
.Thermal  Unit,  and  are  used  as  abbreviations  of  those  words. 
The  British  Thermal  Unit  is  the  unit  of  heat  used  in  this  country 
and  England,  and  may  be  said  to  be  the  amount  of  heat  required 
to  raise  the  temperature  of  one  pound  of  pure  water  from  60  to  61 
degrees  Fahr.  It  is  often  necessary  to  distinguish  between 
B.  T.  U.  used  in  this  country  and  the  French  thermal  unit  used  in 
France  and  most  of  the  countries  of  Europe.  The  French  ther- 
mal unit  is  called  the  calorie,  and  is  the  heat  required  to  raise  the 
temperature  of  one  kilogram  of  water  one  degree  centigrade. 

Safety  at  high  pressure  depends  entirely  upon  the  design, 
material,  and  workmanship,  and  it  is  a  question  that  may  be  re- 
garded as  settled  long  since,  that  a  steam  boiler  properly  con- 
structed and  designed  for  a  working  pressure  of  150  pounds  is  as 
safe  as  a  properly  constructed  boiler  designed  for  eighty  pounds, 
with  the  chances  in  favor  of  the  high  pressure,  for  the  reason  that 
less  care  is  taken  in  selecting  boilers  for  the  ordinary  pressure,  as 
anything  in  the  shape  of  a  boiler  is  regarded,  by  careless  people, 
as  good  enough  for  the  lower  pressures,  with  which  they  have 
become  so  familiar  as  to  become  almost  too  careless. 

SPECIAL  HIGH   PRESSURE  BOILERS. 

The  extending  use  of  compound  steam  engines,  which  make 
necessary  the  employment  of  high  steam  pressures,  calls  for  steam 
boilers  specially  designed  to  successfully  operate  under  working 
pressures  ranging  from  100  to  160  pounds.  These  boilers  must 
be  safe  and  economical  and  of  such  construction  as  to  afford 

26 


402  HANDBOOK    ON    ENGINEERING. 

access  for  examination  and  repair,  moderate  in  first  cost  and 
maintenance  and  of  simplest  possible  form.  Fortunately,  the 
controlling  conditions  are  not  difficult  to  meet,  and  there  are  sev- 
eral well-tried  and  approved  types  of  steam  boilers  from  whi<5h  to 
make  your  selection,  choice  being  governed  by  the  space  tit  dis- 
posal, arrangement  of  plant,  kind  of  fuel  and  other  circum- 
stances. 

TYPES  OF  BOILERS. 

Four  types  that  are  very  succesfully  used,  and  they  represent 
good  practice  for  high  pressure  work,  being  respectively  the  Hori- 
zontal Tubular,  and  Vertical  Fire  Box  Tubular  Boilers.  The  Fire 
Box  Locomotive  Tubular  Boiler  may  safely  be  added  to  this  list 
and  gives  most  excellent  satisfaction. 

THE  WATER  TUBE  BOILER. 

Steam  boilers  must  be  designed  with  reference  to  the  pres- 
sure of  steam  to  be  carried,  and  when  so  designed  and  constructed 
are  quite  as  safe  at  one  pressure  as  another,  preference  being 
given  to  the  type  that  is  simplest  in  form  and  the  least  liable  to 
destruction,  not  so  much  by  reason  of  the  pressure  carried  as  by 
failure  to  provide  for  the  strains  of  expansion  and  contraction 
within  itself. 

HORSE  POWER  OF  BOILERS. 

In  determining  the  proper  size  or  evaporating  capacity  of  a 
boiler  to  supply  steam  for  a  given  purpose,  it  is  necessary  to  con- 
sider the  number  of  pounds  of  dry  steam  actually  required  per 
hour  at  the  stated  pressure.  The  standard  horse  power  rating 
for  any  steam  boiler  is  34^  pounds  of  water  evaporated  (made  into 
steam)  from  feed  water  at  212°  per  hour.  The  total  pounds 
steam  required  for  your  purpose  per  hour  on  this  basis  divided  by 
34 J  will  give  the  standard  boiler  horse  power  required.  Maim- 


HANDBOOK    ON    ENGINEERING.  403 

facturers  of  steam  boilers  sometimes  rate  the  horse  power  of  their 
boilers  by  so  many  square  feet  of  heating  surface  per  horse  power  ; 
8  to  15  sq.  ft.  of  heating  surface,  they  figure,  equals  one  horse 
power.  This  rating  does  not  represent  the  actual  capacity  of  the 
steam  boiler,  the  only  safe  guide  being  the  evaporative  perform- 
ance in  pounds  of  steam  from  water  at  212°  to  steam  at  212°. 
Some  boilers  will  evaporate  this  with  8  sq.  ft.,  some  requiring 
from  15  to  18  sq.  ft.,  hence,  the  absurdity  of  rating  horse  power 
of  boilers  of  unlike  construction  by  the  square  feet  of  heating 
surface.  But  as  the  practice  is  an  old  one  in  the  case  of  the 
well-known  tubular  boiler,  so  deservedly  popular  and  used  more, 
than  any  other  kind,  good  practice  is  to  allow  approximately  as 
follows :  — 

Allow  for  each  Horse  Power  — 

Steam  for  Heating,   etc 15  sq.  ft.  heating  surface. 

For  Plain  Throttle  Engine,      ...      15          "  " 

For  Simple  Corliss  Engine       ...      12          "  " 

For  Compound  Corliss  Condensing  .10  " 

Hence,  a  boiler  for  heating  purposes  or  furnishing  steam  for  — 

Plain  Slide  engine  with  1,500  sq.  ft.  surface,  equals  .  100  H.P. 
For  Simple  Corliss  Engine,  same  boiler  "  .  125  H.  P. 

For  Compound  Engine  'k        .      150  H.  P. 

The  best  method  is  to  compare,  boilers  with  their  evaporative 
ofliciency  and  not  by  heating  surface. 

The  following  is  an  approximate  consumption  of  steam  per 
indicated  horse  power  per  hour  for  engine :  — 

Plain  Slide  Engine 60  to  70  pounds. 

High  Speed  Automatic  Engine 30  to  50       " 

Simple  Corliss  Engine 25  to  35        " 

Compound  Corliss  Engine 15  to  20       u 

Triple  Expansion  Engine 13  to  17       " 


404  HANDBOOK    ON    KXC-JIXKKKING. 

depending  upon  the  horse   power,   steam   pressure,    condition  of 
engine,  load,  etc. 

Each  pound  of  first-class  steam  coal  consumed  under  a  well- 
proportioned  steam  boiler,  well  managed,  should  evaporate  10 
pounds  of  steam  from  water  212°  to  steam  at  212°.  The  average 
boiler  throughout  the  country,  with  ordinary  fuel  and  manage- 
ment, ranges  from  5  to  8  pounds  steam  per  pound  of  coal,  and  it 
would  scarcely  be  safe  to  make  fuel  guarantees  per  horse  power 
of  engine  without  a  counter  guarantee  on  the  part  of  the  pur- 
chaser, when  his  old  boiler  is  used,  that  the  fuel  economy  is  based 
on  an  evaporative  efficiency  of  a  given  pounds  water  evaporated 
per  pound  of  coal  per  hour  of  his  boiler.  The  usual  practice  is 
to  ignore  the  boiler  altogether  and  guarantee  pounds  of  steam 
per  indicated  horse  power  per  hour  used  by  the  engine.  This 
affords  an  exact  method  and  is  not  hampered  by  unknown  con- 
ditions and  places  all  tests  on  an  equal  or  comparative  basis. 

fHE   RATING   OF   BOILERS. 

It  'is  considered  usually  advisable  to  assume  a  set  of  practically 
attainable  conditions  in  average  good  practice,  and  to  take  the 
power  so  obtainable  as  the  measure  of  the  power  of  the  boiler  in 
commercial  and  engineering  transactions.  The  unit  generally 
assumed  has  been  usually  the  weight  of  steam  demanded  per  horse 
power  per  hour  by  a  fairly  good  steam  engine.  '  In  the  time  of 
Watt,  one  cubic  foot  of  water  per  hour  was  thought  fair ;  at  the 
middle  of  the  present  century,  ten  pounds  of  coal  was  a  usual 
figure,  and  live  pounds,  commonly  equivalent  to  about  40  Ibs.  of 
feed  water  evaporated,  was  allowed  the  best  engines.  After  the 
introduction  of  the  modern  forms  of  engine,  this  last  figure  was 
reduced  25  per  cent,  and  the  most  recent  improvements  have  still 
further  lessened  the  consumption  of  fuel  and  of  steam.  By  general 
consent  the  unit  has  now  become  thirty  pounds  of  dry  steam  per 


HANDBOOK    ON    ENGINEERING.  405 

hoj'se  power  per  hour,  which  represents  the  performance  of  uon- 
condensing  engines.  Large  engines,  with  condensers  and  com- 
pound cylinders,  will  do  still  better.  A  committee  of  the 
American  Society  of  Mechanical  Engineers  recommended  thirty 
pounds  as  the  unit  of  boiler  power,  and  this  is  now  generally 
accepted.  They  advised  that  the  commercial  horse  power  be 
taken  as  an  evaporation  of  30  Ibs.  of  water  per  hour  from  a  feed 
water  temperature  of  100°  Fahr.  into  steam  at  70  Ibs.  gauge  pres- 
sure,  which  may  be  considered  equal  to  34J  Ibs.  of  water  evapo- 
ration, that  is,  34  i  Ibs.  of  water  evaporated  from  a  feed  water 
temperature  of  212°  Fahr.  into  steam  at  the  same  temperature. 
This  standard  is  equal  to  33,305  British  thermal  units  per  hour. 
A  boiler  rated  at  any  stated  power  should  be  capable  of 
developing  that  power  with  easy  firing,  moderate  draught  and 
ordinary  fuel,  while  exhibiting  good  economy,  and  at  least 
one-third  more  than  its  rated  power  to  meet  emergencies. 

WORKING  CAPACITY  OF  BOILERS. 

The  capacity  or  horse-power  of  a  boiler,  as  rated  for  purposes 
of  the  trade,  is  commonly  based  upon  the  extent  of  heating 
surface  which  it  contains.  The  ordinary  rating  was  for  a  long 
time  15  sq.  ft.  of  surface  per  horse-power.  At  the  present  time 
most  of  the  stationary  boilers  are  sold  on  the  basis  of  from  10  to 
12  sq.  ft.  per  horse-power,  the  power  referred  to  being  th%e  unit 
of  30  Ibs.  evaporation  per  hour.  This  method  of  rating  is  arbi- 
trary, inasmuch  as  it  is  independent  of  any  condition  pertaining 
to  the  practical  work  of  the  boiler.  The  fact  that  10  or  12  sq. 
ft.  of  surface  is  sold  for  one  horse-power  is  no  guarantee  that  this 
extent  of  surface  will  have  a  capacity  of  one  horse-power  when 
the  boiler  is  installed  and  set  to  work.  The  boiler  in  service 
and  the  boiler  in  the  shop  are  two  entirely  different  things,  and 
where  one  passes  to  the  other,  the  trade  rating  disappears.  New 


4<H)  HANDBOOK    ON    ENGINKKHI-NCJ . 

conditions,  such  as  draft,  grate  surface,  kind  of  fuel  and  man- 
agement, then  take  effect,  and  these  have  a  controlling  influence 
upon  the  working  capacity.  The  working  power  may  be  found 
to  he  much  less  than  the  arbitrary  rate,  or  it  may  be  a  much 
larger  quantity  ;  all  depending  upon  the  surrounding  conditions. 
I  call  attention  to  this  subject,  because  it  is  important  in  sonic 
cases  to  have  a  clearer  understanding  as  to  what  is  the  working 
capacity  of  a  boiler.  Suppose  a  boiler  manufacturer  enters  into 
an  agreement  to  install  a  boiler  which  will  have  a  capacity  of  100 
horse-power.  Suppose  that  on  account  of  poor  draft,  low  grade 
of  fuel,  or  unfavorable  surroundings,  all  of  which  are  known 
beforehand,  the  boiler  develops  the  power  named  only  with  the 
most  careful  handling.  Is  the  working  capacity,  under  the  cir- 
cumstances, 100  horse-power?  Assuredly  not,  for  the  purchaser 
could  not  depend  upon  it  in  ordinary  running  for  that  amount  of 
power.  Yet  the  bulkier  may  claim  that  he  has  fulfilled  his 
contract. 

The  former  boiler  test  committee  of  the  American  Society  of 
Mechanical  Engineers  established  a  working  rate  for  boiler  capac- 
ity which  meets  such  cases  in  a  definite  and  satisfactory  manner. 
They  realized  that  for  the  purpose  of  good  work,  a  boiler  should 
be  capable  of  developing  its  capacity  with  a  moderate  draft  and 
easy  firing ;  and  that  it  should  be  capable  of  doing  one-third  more 
in  cases  of  emergency.  In  other  words,  a  boiler  which  is  sold 
for  100  horse-power  should  develop  133-J  horse-power  under  con- 
ditions giving  a  maximum  capacity.  In  the  instance  cited  above, 
the  boiler  should  have  been  capable  of  giving  100  horse-power 
with  such  ease  that  there  would  be  a  reserve  of  33 1  horse-power 
available  when  urged  to  this  extra  power.  According  to  this 
rule,  the  capacity  of  a  boiler  in  a  working  plant  would  be  found 
by  determining  how  much  water  it  can  e'vaporate  under  conditions 
which  will  give  its  maximum  capacity  ;  that  is,  with  wkle  open 
damper,  with  the  maximum  draft  available  and  with  the  best  con- 


HANDBOOK    ON    ENGINEERING.  407 

ditions  as  to  the  handling  of  the  lire,  and  in  this  way  ascertain 
the  maximum  power  available  under  these  circumstances.  Hav- 
ing found  this  maximum  quantity,  the  working  capacity  or  the 
rated  power  would  be  determined  by  deducting  from  the  maxi- 
mum 25  per  cent.  This  rule,  it  will  be  seen,  does  not  take  into 
account  the  extent  of  the  heating  surface  or  the  trade  rating,  but 
it  deals  solely  with  the  capabilities  of  the  boiler  under  the  con- 
ditions which  pertain  to  its  work. 

CODE  OF  RULES  FOR  BOILER  TESTS. 

Starting  and  stopping  a  test. —  A  test  should  last  at  least 
ten  hours  of  continuous  running,  and  twenty-four  hours  whenever 
practicable.  The  conditions  of  the  boiler  and  furnace  in  all 
respects  should  be,  as  nearly  as  possible,  the  same  at  the  end 
as  at  the  beginning  of  the  test.  The  steam  pressure  should  be 
the  same  ;  the  water  level  the  same  ;  the  fire  upon  the  grates 
should  be  the  same  in  quantity  and  condition  ;  and  the  walls,  flues, 
etc.,  should  be  of  the  same  temperature.  To  secure  as  near  an 
approximation  to  exact  conformity  as  possible  in  conditions  of 
the  fire  and  in  the  temperature  of  the  walls  and  Hues,  the  follow- 
ing method  of  starting  and  stopping  a  test  should  be  adopted :  — 

Standard  method*  —  Steam  being  raised  to  the  working  pres- 
sure, remove  rapidly  all  the  fire  from  the  grate,  close  the  damper, 
clean  the  ash-pit,  and,  as  quickly  as  possible,  start  a  new  fire  with 
weighed  wood  and  coal,  noting  the  time  of  starting  the  test  and 
the  height  of  the  water  level  while  the  water  is  in  a  quiescent 
state,  just  before  lighting  the  fire.  At  the  end  of  the  test,  re- 
move the  whole  fire,  clean  the  grates  and  ash-pit,  and  note  the 
water-level  when  the  water  is  in  a  quiescent  state  ;  record  the  time 
of  hauling  the  fire  as  the  end  of  the  test.  The  water-level  should 
be  as  nearly  as  possible  the  same  as  at  the  beginning  of  the  test. 
If  it  is  not  the  same,  a  correction  should  be  made  by  computa- 


408  HANDBOOK    ON    ENGINEERING. 

tion,  and  not  by  operating  pump  after  test  is  completed.  It  will 
generally  be  necessary  to  regulate  the  discharge  of  .steam  from  the 
boiler  tested  by  means  of  the  stop-valve  for  a  time  while  fires  are 
being  hauled  at  the  beginning  and  at  the  end  of  the  test,  in  order 
to  keep  the  steam  pressure  in  the  boiler  at  those  times  up  to  the 
average  during  the  test. 

Alternate  method*  —  Instead  of  the  standard  method  above 
described,  the  following  may  be  employed  where  local  conditions 
render  it  necessary :  At  the  regular  time  for  slicing  and  cleaning 
fires  have  them  burned  rather  low,  as  is  usual  before  cleaning, 
and  then  thoroughly  cleaned  ;  note  the  amount  of  coal  left  on  the 
grate  as  nearly  as  it  can  be  estimated  ;  note  the  pressure  of  steam 
and  the  height  of  the  water-level  —  which  should  be  at  the  medium 
height  to  be  carried  throughout  the  test  —  at  the  same  time  ;  and 
note  this  time  as  the  time  for  starting  the  test.  Fresh  coal  which 
has  been  weighed,  should  now  be  fired.  The  ash-pits  should  be 
thoroughly  cleaned  at  once  before  starting.  Before  the  end  of  the 
test  the  fires  should  be  burned  low,  just  as  before  the  start,  and 
the  fires  cleaned  in  such  a  manner  as  to  leave  the  same  amount 
of  lire,  and  in  the  same  condition,  on  the  grates  as  on  the  start. 
The  water-level  and  steam  pressure  should  be  brought  to  the  same 
point  as  at  the  start,  and  the  time  of  the  ending  of  the  test  should 
be  noted  just  before  fresh  coal  is  fired. 

DURING  THE  TEST. 

Keep  the  conditions  uniform.  —  The  boiler  should  be  run  con- 
tinuously without  stopping  for  meal-times,  or  for  rise  or  fall  of 
pressure  of  steam  due  to  change  of  demand  for  steam.  The 
draught  being  adjusted  to  the  rate  of  evaporation  or  combustion 
desired  before  the  test  is  begun,  it  should  be  retained  constant 
during  the  test  by  means  of  the  damper.  If  the  boiler  is  not  con- 
nected to  the  same  steam-pipe  with  other  boilers,  an  extra  outlet 


HANDBOOK    ON     K\(  J  IN  KKKING.  409 

for  steam  with  valve  in  same  should  be  provided,  so  that  in  case 
the  pressure  should  rise  to  that  at  which  the  safety  valve  is  set,  it 
may  he  reduced  to  the  desired  point  by  opening  the  extra  outlet, 
without  checking  the  lire.  If  the  boiler  is  connected  to  a  main 
steam-pipe  with  other  boilers,  the  safety  valve  on  the  boiler  being 
tested  should  be  set  a  few  pounds  higher  than  those  of  the  other 
boilers,  so  that  in  case  of  a  rise  in  the  pressure  the  other  boilers 
may  blow  off,  and  the  pressure  be  reduced  by  closing  their  dam- 
pers, allowing  the  damper  of  the  boiler  being  tested  to  remain 
open,  and  firing  as  usual.  All  the  conditions  should  be  kept  as 
nearly  uniform  as  possible,  such  as  force  of  draught,  pressure  of 
steam  and  height  of  water.  The  time  of  cleaning  the  lires  will 
depend  upon  the  character  of  the  fuel,  the  rapidity  of  combustion 
and  the  kind  of  grates.  When  very  good  coal  is  used  and  the 
combustion  not  too  rapid,  a  ten-hour  test  may  be  run  without  any 
cleaning  of  the  grates,  other  than  just  before  the  beginning  and 
just  before  the  end  of  the  test.  But  in  case  the  grates  have  to  be 
cleaned  during  the  test,  the  intervals  between  one  cleaning  and 
another  should  be  uniform. 

Keeping  the  records*  —  The  coal  should  be  weighed  and 
delivered  to  the  iiremen  in  equal  portions,  each  sufficient  for  about 
one  hour's  run,  and  a  fresh  portion  should  not  be  delivered  until 
the  previous  one  has  all  been  fired.  The  time  required  to  con- 
sume each  portion  should  be  noted,  the  time  being  recorded  at  the 
instant  of  tiring  the  first  of  each  new  portion.  It  is  desirable  that 
at  the  same  time  the  amount  of  water  fed  into  the  boiler  should 
be  accurately  noted  and  recorded,  including  the  height  of  the 
water  in  the  boiler,  and  the  average  pressure  of  steam  and  tem- 
perature of  feed  during  the  time.  By  thus  recording  the 
amount  of  water  evaporated  by  successive  portions  of  coal,  the 
record  of  the  test  may  be  divided  into  several  divisions,  if  desired 
at  the  end  of  the  test,  to  discover  the  degree  of  uniformity  of  com- 
bustion, evaporation  and  economy  at  different  stages  of  the  test. 


410  HANDBOOK    ON    ENGINEERING. 

PRIMING  TESTS. 

In  all  tests  in  which  accuracy  of  results  is  important,  calori- 
meter tests  should  be  made  of  the  percentage  of  moisture  in  the 
steam,  or  of  the  degree  of  superheating.  At  least  ten  such 
tests  should  be  made  during  the  trial  of  the  boiler,  or  so  many  as 
to  reduce  the  probable  average  error  to  less  than  one  per  cent, 
and  the  linal  records  of  the  boiler  tests  corrected  according  to  the 
average  results  of  the  calorimeter  tests.  On  account  of  the 
difficulty  of  securing  accuracy  in  these  tests,  the  greatest  care 
should  be  taken  in  the  measurements  of  weights  and  temperatures. 
The  thermometers  should  be  accurate  to  within  a  tenth  of  one 
degree,  and  the  scales  on  which  the  water  is  weighed  to  within 
one-hundredth  of  a  pound. 

ANALYSES  OF  GASES. 

Measurement  of  air  supply,  etc*  —  In  tests  for  purposes  of 
scientific  research,  in  which  the  determination  of  all  the  variables 
entering  into  the  test  is  desired,  certain  observations  should  be 
made  which  are  in  general  not  necessary  in  tests  for  commercial 
purposes.  These  are  the  measurements  of  the  air  supply,  the 
determination  of  its  contained  moisture,  the  measurement  and 
analysis  of  the  Hue  gases,  the  determination  of  the  amount  of  heat 
lost  by  radiation,  of  the  amount  of  infiltration  of  air  through  the 
setting,  the  direct  determination  by  calorimeter  experiments  of 
the  absolute  heating  value  of  the  fuel,  and  (by  condensation  of 
all  the  steam  made  by  the  boiler)  of  the  total  heat  imparted  to 
the  water. 

The  analysis  of  the  Hue  gases  is  an  especially  valuable 
method  of  determining  the  relative  value  of  different  methods  of 
firing,  or  of  different  kinds  of  furnaces.  In  making  these 
analyses,  great  care  should  be  taken  to  procure  average  samples 


HANDBOOK    ON    ENGINEERING. 


411 


since  the  composition  is  apt  to  vary  at  different  points  of  the  Hue, 
and  the  analyses  should  be  intrusted  only  to  a  thoroughly  com- 
petent chemist,  who  is  provided  with  complete  and  accurate 
apparatus.  As  the  determination  of  the  other  variables  men- 
tioned above  are  not  likely  to  be  undertaken  except  by  engineers 
of  high  scientific  attainments,  and  as  apparatus  for  making  them 
is  likely  to  be  improved  in  the  course  of  scientific  research,  it  is 
not  deemed  advisable  to  include  in  this  code  any  specific  direc- 
tions for  making  them. 

RECORD  OF  THE  TEST. 

A  "  log n   of  the  test   should    be  kept  on   properly   prepared 
blanks,  containing  headings  as  follows :  — 


PRESSURES. 

T  E  M  P  E  R  A  T  U  R  E  S  . 

FUEL.. 

FEED  WATER. 

% 

« 

^ 

g 

*M 

TIME. 

Baromete  i 

03 

'or 

1 
S 

0) 

Draft  gauj 

Extemal  a 

o 
o 

'o 

Flue. 
F.eecl  wate 

02 

1 

Pounds. 

H 

o 
-  o 

Cft 

1 

j 

1 

'     i 

REPORTING  THE  TRIAL. 

The  final  results  should  be  recorded  upon  a  properly  prepared 
blank,  and  should  include  as  many  of  the  following  items  as  are 
adapted  for  the  specific  object  for  which  the  trial  is  made.  The 
items  marked  with  a  *  may  be  omitted  for  ordinary  trials,  but  are 
desirable  for  comparison  with  similar  data  from  other  sources. 


412 


HANDBOOK    ON    ENGINEERING 


Resources  of  the  trials  of   a 

Boiler  at 

To  determine ; 

1.  Date  of  trial 

2.  Duration  of  trial 

DIMENSIONS    AND    PROPORTIONS. 

3.  Grate-surface  wide         long         area 

4.  Water-heating  surface     ...... 

5.  Superheating  surface       .      .      .      .      . 

6.  Ratio  of  water-heating  surface   to  grate- 

surface      

AVERAGE    PRESSURES. 

7.  Steam  pressure  in  boiler,  by  gauge     .     . 
*8.  Absolute  steam  pressure       .      .      .     •     • 
*9.  Atmospheric  pressure,  per  barometer 
10.  Force  of  draught  in  inches  of  water  . 

AVERAGE    TEMPERATURES. 

*  11 .   Of  external  air 

*15.   Of  lire-room 

*13.  Of  steam 

14.  Of  escaping  gases 

15.  Of  feed-water 

FUEL. 

16.  Total  amount  of  coal  consumed     . 

17.  Moisture  in  coal 

18.  Dry  coal  consumed V  >_. 

19.  Total  refuse,  dry  pounds  equals     . 

20.  Total  combustible  (dry  weight  of   coal, 

item   18,  less  refuse,  item  19)    . 
*21.   Dry  coal  consumed  per  hour 
*22.   Combustible  consumed  per  hour    . 


hours, 
hours. 

Sq.  ft. 
Sq.  ft. 
Sq.  ft. 


Ibs. 
Ibs. 
in. 
in. 

deg. 
deg. 
deg. 
deg. 
deg. 

Ibs. 
per  cent. 

Ibs. 
per  cent. 

Ibs. 
Ibs. 
Ibs. 


HANDBOOK    OX    ENGINEERING.  413 

RKSri/l'S    OK     CALORIMKTRIC    TESTS. 

23.  Quality  of  steam,  dry  steam  being  taken 

as  unity  . 

24.  Percentage  of  moisture  in  steam     .      .      .  percent. 
2T).  'Number  of  degrees  superheated      .      .      .  cleg. 

*  WATER. 
2<>.   Total  weight  of  water  pumped  into  boiler 

and  apparently  evaporated    ....  Ibs. 

27.   Water  actually  evaporated,  corrected  for 

quality  of  steam IDS. 

2*.   Equivalent     water    evaporated    into    dry 

steam  from  and  at  212°  F Ibs. 

*2i>.   Equivalent  total  heat  derived  from  fuel 

in  B.  T.  U B.  T.  U. 

*30.   Equivalent    water    evaporated      in     dry 

steam  from  212°  F.  per  hour     ...  Ibs. 

-    ECONOMIC    EVAPORATION. 

31.  Water  actually  evaporated  per  pound  of 

dry    coal,    from    actual    pressure    and 

temperature        .     • Ibs. 

32.  Equivalent  water  evaporated  per  pound 

of* dry  coal,  from  212°  F Ibs. 

33.  Equivalent  water  evaporated  per  pound 

of  combustible  from  and  at  212°  F.      .  Ibs. 

COMMERCIAL    EVAPORATION. 

34.  Equivalent  water  evaporated  per  pound 

of  dry  coal  with  one-sixth  refuse,  at  70 
Ibs.  gauge  pressure,  from  temperature  of 
100°  F.,  equals  item  tests  33  X.  0.7249 
pounds Ibs. 

t  corrected  for   inequality  of   water  level  and  of  steam   pressure   at 
beginning  and  end  of  test. 


414 


HANDBOOK    ON    ENGINEERING. 


RATE    OF    COMBUSTION. 

35.  Dry  coal  actually  burned  per  sq.  foot  of 

grate-surface  per  hour 

Per  sq.  ft.  of  grate 
Consumption      of      dry         surface 

coal  per  hour.  Coal  Per  sq.  ft.  of  water 
assumed  with  one-  [  heating  surface  . 
sixth  refuse.  Per  sq.  foot  of  least 

area  for  draught. 


*36 

*37 
*38 


39, 


*40. 
*41. 

*42, 


KATE -OF    EVAPORATION. 

Water  evaporated  from  and  at  212°  F.  per 
square  foot  of  heating  surface  per  hour. 

Per  sq.  ft.  of  grate 
Water     evaporated    per 

hour  from  temperature 
of  100°  F.  into  steam 
of  70  Ibs.  gauge  pres- 
sure. 


surface 

Per  sq.  ft.  of  heat- 
ing surface 

Per  sq.  ft.  of  least 
area  for  draught. 


COMMERCIAL    HORSE    POWER. 

43.  On  basis  of  30  Ibs.  of  water  per  hour 

evaporated  from  temperature  of  100°  F. 
into  steam  of  70  Ibs.  gauge  pressure 
(34J  Ibs.  from  and  at  212°)  .  .  . 

44.  Horse-power,    builders'     rating   at 

sq.  ft.  per  horse-power 

45.  Per  cent  developed  above  or  below  rating 


Ibs. 
Ibs. 

Ibs. 
Ibs. 


Ibs. 
Ibs. 
Ibs. 


H.  P. 


per  cent. 


*  NOTE.  Items  20,  22,  33,  34,  36,  37,  38  are  of  little  practical  value. 
For  if  the  result  proves  to  be  less  satisfactory  than  expected  on  the 
actual  coal,  it  is  easy  for  an  expert  fireman  to  decrease  No.  20  by  simply 
taking  out  some  partly  consumed  coal  in  cleaning  fires,  and  thus  make  a 
fine  showing  on  that  simply  ideal  or  theoretical  unit,  the  u pound  com- 
bustible." The  question  at  issue  is  always  what  can  be  done  with  an 
actual  coal,  not  the  "  assumed  coal  "  of  Hems  34,  36,  37  and  38, 


HANDBOOK    ON    ENGINEERING.  415 

DEFINITIONS    AS    APPLIED    TO  BOILERS   AND    BOIUBR 
flATERIALS. 

Cohesion  is  that  quality  of  the  particles  of  a  body  which  causes 
them  to  adhere  to  each  other,  and  to  resist  being  torn  apart. 

Curvilinear  seams*  —  The  curvilinear  seams  of  a  boiler  are 
those  around  the  circumference. 

Elasticity  is  that  quality  which  enables  a  body  to  return  to  its 
original  form  after  having  been  distorted,  or  stretched  by  some 
external  force. 

Internal  radius* — The  internal  radius  is  one-half  of  the  diam- 
eter, less  the  thickness  of  the  iron.  To  find  the  internal  radius 
of  a  boiler,  take  one-half  of  the  external  diameter  and  substract 
the  thickness  of  the  iron. 

Limit  of  elasticity*  —  The  extent  to  which  any  material  may  be 
stretched  without  receiving  a  permanent  "  set." 

Longitudinal  seams*  —  The  seams  which  are  parallel  to  the 
length  of  a  boiler  are  called  the  longitudinal  seams. 

Strength  is  the  resistance  which  a  body  opposes  to  a  disinte- 
gration or  separation  of  its  parts. 

Tensil  strength  is  the  absolute  resistance  which  a  body  makes 
to  being  torn  apart  by  two  forces  acting  in  opposite  direc- 
tions. 

Crushing  strength  is  the  resistance  which  a  body  opposes  to 
being  battered  or  flattened  down  by  any  weight  placed  upon  it. 

Transverse  strength  is  the  resistance  to  bending  or  flexure,  as 
it  is  called. 

Torsional  strength  is  the  resistance  which  a  body  offers  to 
any  external  force  which  attempts  to  twist  it  round. 

Detrusive  strength  is  the  resistance  which  a  body  offers  to 
being  clipped  or  shorn  into  two  parts  by  such  instruments  as 
shears  or  scissors. 

Resilience  or   toughness  is    another  form    of   the    quality   of 


416  HANDBOOK    ON 

strength;  it  indicates  that  a  body  will  manifest  ;i  m-tain  degree 
of  flexibility  before  it  can  be  broken  ;  hence,  that  body  which 
bends  or  yields  most  at  the  time  of  fracture  is  the  toughest. 

Working  strength. —  The  term  "  working  strength  "  implies 
a  certain  reduction  made  in  the  estimate  of  the  strength  of  ma- 
terials, so  that  when  the  instrument  or  machine  is  put  to  use,  it 
may  be  capable  of  resisting  a  greater  strain  than  it  is  expected  on 
the  average  to  sustain. 

Safe  working  pressure,  or  safe  load*  —  The  safe  working  pros- 
sure  of  steam-boilers  is  generally  taken  as  *  of  the  bursting  pres- 
sure, whatever  that  may  be. 

Strain  in  the  direction  of  the  grain,  means  strain  in  the  direc- 
tion in  which  the  iron  has  been  rolled  :  and  in  the  process  of  man- 
ufacturing boiler-plates,  the  direction  in  which  the  libres  of  the 
iron  are  stretched  as  it  passes  between  the  rolls. 

Stress.  —  By  the  term  "  stress  "  is  meant  the  force  which  acts 
directly  upon  the  particles  of  any  material  to  separate  them. 

HEAT  AND   STEAM. 

The  steam  engine  is  a  machine  for  the  conversion  of  heat  into 
power  in  motion.  The  heat  is  generated  by  the  combustion  of 
fuel ;  the  transmission  is  accomplished  through  the  agency  of 
steam  ;  the  power  is  made  available  and  brought  under  control  by 
means  of  the  engine. 

The  effect  of  heat  upon  water  is  to  vaporize,  it,  if  there  be  inten- 
sity enough,  the  heat  will,  under  proper  conditions,  cause  water  to 
boil;  the  vapor  produced  by  boiling  is  called  steam,  and  steam 
under  pressure  is  a  product  which  is  the  end  and  aim  of  that  por- 
tion of  that  steam  engine  known  as  the  boiler  and  furnace.  The 
steam  engine  then  is  to  be  considered  as  a  form  of  the  heat 
engine ;  of  which  the  furnace,  boiler,  and  the  engine  itself  are  to 
be  regarded  as  separate  portions  of  the  same  mechanism. 


HANDBOOK    ON    ENGINEERING.  417 

The  conditions  demanded  upon  economic  grounds  to  secure 
the  highest  ellicioncy  in  the  steam  engine  are:  — , 

1.  A  proper  construction  of  the  furnace  so  as   to   secure  the 
perfect  combustion  of  fuel. 

2.  The  heat  generated  in  the  furnace  must  be  transferred  to  the 
water  in  the  boiler  without  loss. 

3.  The  circulation  in  the  boiler  must  be  so  complete  that  the 
heat  from   the  furnace   may   be   quickly  and  thoroughly  diffused 
throughout  the  whole  body  of  water. 

4.  The  construction  of  an  engine  that  will  use  the  steam  with- 
out loss  of  heat,  except  so  much  as  may  be  necessary  to  perform 
work  required  of  the  engine. 

5.  The  recovery  of  heat  from  exhaust  steam. 

6.  The  absence  of  friction  and  back  pressure  in  the  working  of 
the  engine. 

It  is  superfluous  to  say  that  these  conditions  are  not  fulfilled 
in  any  engine  of  the  present  day.  At  best  the  combustion  of 
fuel  is  only  approximately  perfect,  the  losses  being  due  to  several, 
causes,  among  which  are,  —  unburned  fuel  falling  through  the 
spaces  in  the  grates  and  mingling  with  the  ashes.  This,  with, 
some  kinds  of  coal,  and  improper  firing,  amounts  to  a  large 
percentage  of  the  furnace  waste.  It  is  not  possible  with  any 
present  method  of  setting  boilers  to  transfer  all  the  heat  of  the 
furnace  to  the  water  in  the  boiler ;  nor  can  there  be,  for  the 
reason  that  the  temperature  of  the  escaping  gases  must  not  be 
lower  than  that  of  the  steam  in  the  boilers,  or  direct  loss  will  result 
in  the  radiation  of  heat  from  the  tubes  or  flues  in  the  boiler,  by 
thus  reheating  the  gases  to  the  steam  temperature.  If  the  steam 
pressure  is  80  Ibs.  per  square  inch  above  the  atmosphere,  the  cor- 
responding temperature  due  to  this  pressure  is  324°  Fahr.  The 
temperature  of  the  escaping  gases  ought  not,  therefore,  to  be  less 
than  350°  Fahr.,  where  they  leave  the  boiler  flues  or  tubes  to  pass 

off  into  the  chimney.     If  the  temperature  of  the  furnace  be  taken 

27    - 


418  HANDBOOK    OX    ENGINEERING. 

at  2,000°  Fahr.,  and  the  escaping  gases  at  400°  Kahr.,  it  will  be 
seen  that  one-fifth  of  the  heat  generated  in  the  furnace  is  passing 
off  without  performing  work.  This  is  a  very  great  loss,  and 
these  figures  understate,  rather  than  correctly  give,  the  loss  from 
this  one  source.  Efforts  have  been  made  to  utilize  the  tempera- 
ture of  these  waste  gases  by  making  them  heat  feed  water  by 
means  of  coils,  or  by  that  particular  disposition  of  pipes  and 
connection  known  as  an  economizer.  Others  have  turned  it  into 
account  by  making  it  heat  the  air  supplied  the  fuel  on  the  grates. 
Any  heat  so  reclaimed  is  money  saved,  provided  it  does  not  cost 
more  to  get  it  than  it  is  worth  in  coal  to  generate  a  similar  quan- 
tity of  heat.  It  is  doubtful  whether  the  loss  in  this  particular 
direction  can  be  brought  below  20  per  cent  of  the  fuel  burned,  at 
least,  by  any  method  of  saving  now  known. 

The  loss  by  bad  firing  and  by  a  bad  construction  of  furnace 
is  often  a  large  one.  It  has  been  demonstrated  experimentally 
that  20  to  30  per  cent  of  fuel  can  be  saved  by  a  proper  construc- 
tion and  operation  of  the  furnace.  The  direct  causes  of  loss  are, 
too  low  temperature  of  furnace  for  properly  burning  fuels,  espe- 
cially such  as  are  rich  in  hydro-carbon  gases  ;  or,  by  the  admis- 
sion of  too  much  cold  air  over  or  back  of  the  fire ;  or,  by  the 
admission  of  too  little  air  under  the  fire  so  that  carbonic  oxide  gas 
is  generated  instead  of  carbonic  acid  gas,  the  former  being  a 
product  of  incomplete,  the  latter  the  product  of  complete 
combustion.  The  relative  heating  powers  of  fuel  burned,  resulting 
in  the  production  of  either  of  these  two  gases  being  as  follows  :  — 

Heat  Units. 

1  pound  of  carbon  burned  to  carbonic  acid  gas   .     .      14,500 
1  pound  of  carbon  burned  to  carbonic  oxide  .     .      .       4,500 

Units  of  heat  lost  by  burning  to  carbonic  oxide       .      10,000 
It  will  be  seen  that  here  is  an  enormous  source  of  loss,  and  all 
that  is  required  to  prevent  it  is  a  proper  construction  of  furnace. 


HANDBOOK    ON    ENGINEERING.  419 

Smoke  is  u  nuisance  which  ought  to  be  prohibited  by  stringent 
legislation.  There  is  no  good  reason  for  its  polluting  presence  in 
the  atmosphere,  defiling  everything  with  which  it  comes  in  con- 
tact. Smoke  regarded  as  a  source  of  direct  loss  is  greatly  over- 
estimated ;  the  fact  is,  the  actual  amount  of  coal  lost  to  produce 
smoke  is  very  trilling.  The  presence  of  smoke  indicates  a  low 
temperature  of  f ur.nace  or  combustion  chamber ;  if  the  temper- 
ature were  sufficiently  high  and  the  furnace  properly  constructed, 
smoke  could  not  be  generated.  The  prevention  of  smoke  is 
easily  accomplished,  and  with  it  a  more  economical  combustion 
of  hydro-carbon  fuels. 

Radiation*  —  A  considerable  loss  of  heat  occurs  by  radiation 
from  the  furnace  walls ;  this  may  be  prevented  in  part  by  making 
the  walls  hollow,  with  an  air  space  between.  If  a  force  blast  is 
used  the  air  may  be  admitted  at  the  back  end  of  the  boiler-setting 
and  by  passing  through  between  the  walls  will  become  heated, 
and  if  conveyed  into  the  ash  pit  at  a  high  temperature  will  greatly 
assist  combustion  and  thus  tend  to  a  higher  economy. 

Air  required.  —  In  regard  to  the  quantity  of  air  required,  it 
will  vary  somewhat  with  the  fuel  used,  but  in  general,  12  pounds 
of  air  are  sufficient  to  completely  burn  one  pound  of  coal ;  prac- 
tically, however,  15  to  25  pounds  are  furnished,  being  largely  in 
excess  of  that  which  the  fire  can  use,  and  must  pass  off  with  the 
gases  as  a  waste  product.  This  surplus  air  enters  cold  and 
leaves  the  furnace  heated  to  the  same  temperature  as  that  of  the 
legitimate  and  proper  products  of  combustion,  and  thus  directly 
operates  to  the  lowering  of  the  furnace  temperature. 

Measurement  of  heat*  —  A  heat  unit  is  that  quantity  of  heat 
necessary  to  raise  the  temperature  of  one  pound  of  water  one 
degree,  from  39°  to  40°  Fahr.,  this  being  the  temperature  of  the 
greatest  density  of  water.  A  thermal  unit,  a  heat  unit,  or  unit 
of  heat,  all  mean  the  same  thing.  Experiments  have  been  made 
to  determine  the  mechanical  equivalent  of  a  heat  unit,  and  it  is 


420  HANDBOOK    ON    ENGINEERING. 

found  to  be  equal  to  772  pounds  raised  one  foot  high.  This  is 
sometimes  called  "Joule's  equivalent,"  after  Dr.  Joule,  of 
England ;  it  is  also  known  as  the  dynamic  value  of  a  heat  unit. 
Knowing  the  number  of  heat  units  in  a  pound  of  coal  enables 
us  to  calculate  the  amount  of  work  it  should  perform.  Let  us 
suppose  a  pound  of  coal  to  be  burned  to  carbonic  acid  gas, 
and  to  develop  during  its  combustion  14,000  heat  units,  then : 
14,000x772  equals  10,808,000  foot  pounds. 

That  is  to  say,  if  one  pound  of  coal  were  burned  under  the 
above  conditions  it  would  have  a  capacity  for  doing  work  repre- 
sented by  the  lifting  of  ten  millions  of  pounds  one  foot  high 
against  the  action  of  gravity.  Suppose  this  to  be  done  in  one 
hour,  then  we  should  expect  to  get  from  one  pound  of  coal  an 
equivalent  of  5.45  H.  P.  It  is  well  known  that  only  a  very 
small  fraction  of  such  equivalent  is  secured  in  the  very  best 
modern  practice.  The  question  is,  where  does  this  heat  go, 
and  why  is  it  so  small  a  portion  of  it  is  actually  utilized  ?  The 
losses  may  be  accounted  for  in  several  ways,  and,  perhaps,  as 
follows :  — 

The   heat  wasted  in  the  chimney     .      .      .      .     25  per  cent. 

Through  bad  firing .         10       " 

Heat  accounted  for  by  the  engine  (not  indicated)      10       " 
Heat  by  exhaust  steam     .......     55       " 

100  per  cent. 

This  is  about  2  pounds  of  coal  per  hour  per  indicated  horse 
power,  which  is  regarded  as  a  very  high  attainment,  and  is 
seldom  reached  in  ordinary  cut-off  engines.  It  requires  good 
coal,  good  firing,  and  an  economical  engine  to  get  an  indicated 
horse  power  from  two  pounds  of  coal  burned  per  hour.  As 
coal  varies  in  quality  it  is  a  better  plan  to  deduct  the  ashes 
and  other  incombustible  matter,  and  take  the  net  combustible 
as  a  basis  of  comparison.  The  best  coal  when  properly  burned 


HANDBOOK    ON    ENGINEERING.  421 

is  capable  of  evaporating  15  pounds  of  water  from  and  at  a 
temperature  of  212°  Fahr.  The  common  evaporation  is  about 
half  that  amount,  and  with  the  best  improved  furnaces  and  care- 
ful management,  it  is  seldom  that  10  pounds  of  water  is  exceeded, 
•and  is  to  be  regarded  as  a  high  rate  of  evaporation.  In  experi- 
mental tests,  12  pounds  have  been  reported,  but  it  is  doubtful 
whether  there  is  any  steam  boiler  and  furnace  which  is  con- 
stantly yielding  any  such  results. 

Circulation  of  water  in  a  boiler  is  a  very  important  feature  to 
secure  the  highest  evaporative  results.  Other  things  being  equal, 
the  boiler  which  affords  the  best  circulation  of  water  will  be  found 
to  be  the  most  economical  in  service.  Circulation  is  greatly  hin- 
dered in  some  boilers  by  having  too  many  tubes ;  in  others,  by 
introducing  in  the  water  space  of  the  boiler  too  many  stays  and 
making  the  water  spaces  too  narrow.  To  secure  the  highest 
economy  there  must  be  thorough  circulation  from  below  upwards, 
in, the  boiler.  There  is  no  doubt  that  a  great  deal  of  heat  is  lost 
because  the  construction  is  such  as  to  hinder  a  free  flow  of  water 
around  the  tubes  and  sides  of  the  boiler. 

The  construction  of  an  engine  that  will  use  steam  without  loss 
of  heat,  except  so  much  as  may  be  necessary  to  perform  work 
required  of  it,  is  a  physical  impossibility.  Among  the  sources  of 
loss  ill  an  engine  are :  radiation,  condensation  of  steam  in  un- 
jacketed  cylinders,  and  the  enormous  loss  of  heat  occasioned  by 
exhausting  the  steam  into  the  atmosphere. 

Radiation  is  usually  classed  among  the  minor  losses  in  a  steam 
engine.  There  is  a  considerable  loss  of  heat  caused  by  radiation 
from  steam  boilers  and  pipes  exposed  to  the  atmosphere,  and  not 
protected  by  a  suitable  covering.  Much  of  this  heat  may  be 
saved  by  employing  a  non-conducting  material  as  a  covering, 
which,  though  not  preventing  all  radiation,  will  save  enough  heat 
to  make  its  application  economical.  It  is  well  known  that  some 
bodies  conduct  and  radiate  heat  less  rapidly  than  others,  but  it 


422  HANDBOOK    ON    ENGINEERING. 

must  not  be  understood  thut  the  absolute  value  of  such  it  Cover- 
ing is  inversely  proportioned  to  the  conducting  power  of  the 
material  employed,  because,  in  its  application,  the  outer  surface 
is  enlarged  and  the  radiation  will  be  going  on  less  actively  at  any 
given  point,  but  the  enlarged  surface  exposed  reduces  somewhat 
the  apparent  gain. 

SELECTION  OF  A  BOILER. 

The  selection  of  a  boiler  for  a  particular  service  will  naturally 
suggest  the  following  questions  :  - 

1.  What  kind  of  a  boiler  shall  it  be? 

2.  Of  what  material  shall  it  be  made? 

3.  What  size  shall  it  be  in  order  to  furnish  a  certain  power? 
In  reply  to  the  first  question,  it  is  to  be  expected  there  will  be 

wide  differences  of  opinion,  varying  with  the  locality,  usage,  and 
service  for  which  it  is  intended.  One  of  the  first  things  to  be 
taken  into  account  in  the  selection  of  a  boiler  is  the  quality  of 
water  to  be  used  in  it  for  generating  steam.  If  the  water  is  pure, 
then  it  makes  little  difference  what  kind  of  boiler  be  selected,  so 
far  as  incrustation  affects  selection.  If  the  water  is  hard  and 
will  deposit  scale  upon  evaporation,  then  a  boiler  should  be 
selected  which  will  admit  of  thorough  inspection  and  removal  of 
any  deposit  formed  within  it. 

For  hard  water,  the  ordinary  tine  boiler  will*  be  found  a  good 
one,  as  it  is  favorable  to  a  thorough  circulation  of  water,  and 
permits  easy  access  to  all  parts  of  it  for  examination  and  clean- 
ing. It  does'  not,  however,  present  the  extent  of  heating  surface 
for  a  given  space  that  tubular  boilers  offer  ;  but  with  hard  water 
the  boiler  is  quite  as  economical  if  kept  in  good  condition. 

The  difficulty  with  tubular  boilers  when  used  in  connection 
with  hard  water  is  that  the  tubes  will  in  a  short  time  become 
coated  with  scale  ;  this  prevents  the  transmission  of  heat,  not 
only,  but  impairs  the  circulation  of  the  water  around  them. 


HANDBOOK    ON    ENGINEERING.  423 

Both  of  these  are  opposed  to  economy  in  the  fact  that  it  requires 
more  coal  to  generate  a  given  weight  of  steam  in  the  first  case; 
and  second,  by  reason  of  deficient  circulation  the  plates  over  the 
(ire  are  likely  to  become  overheated  and  burnt  and  so  become 
dangerous  ;  thus  directly  contributing  to  accident  or  disaster. 

The  matter  of  circulation  in  boilers  is  one  which  should  have 
careful  sit  tendon  in  making  a  selection.  There  is  little  trouble  in 
this  regard  with  any  of  the  ordinary  types  of  boilers  so  long  as 
they  are  clean  and  new,  and  properly  proportioned.  Nor  is  there 
likely  to  be  any  difficulty  thereafter  if  the  water  is  soft  and  clean. 
Circulation  is  often  seriously  impaired  by  putting  in  too  many 
tubes  in  a  boiler,  the  effect  of  which  is  to  so  fill  up  the  space  that 
the  heated  particles  of  water  forcing  their  way  upwards  from 
below  meet  with  so  much  resistance  that  they  can  hardly  over- 
come it,  and  the  result  is  that  a  boiler  does  not  furnish  from  one- 
fourth  to  one-half  as  much  steam  for  a  given  weight  of  fuel  as  it 
should,  from  this  very  cause. 

Boilers  intended  for  use  in  distant  localities  where  the  facilities 
for  repairs  are  meager  or  entirely  wanting,  and  fuel  low  priced, 
should  be  of  the  simplest  description.  Cylinder  boilers  or  two- 
flue  boilers  will  perhaps  be  found  most  suitable.  These  are 
largely  used  by  coal  miners,  blast  furnaces,  saw  mills,  and  other 
branches  of  industry,  which  must,  of  necessity,  be  removed  from 
the  larger  towns  and  engineering  work  shops. 

In  selecting  a  boiler  for  a  mill  of  any  kind  where  they  burn 
shavings  or  offal,  or  any  other  place  in  which  the  fuel  is  of 
a  similar  description  and  the  firing  irregular,  there  should  be 
large  water  capacity  in  the  boiler  that  it  may  act  as  a  reser- 
voir of  power  in  much  the  same  way  that  a  fly  wheel  acts  as 
a  regulator  for  a  steam  engine.  It  is  a  common  notion  among 
wood- workers  that  firing  with  shavings  or  light  fuel  is  "  easy 
on  the  boiler."  •  There  is  abundant  iveason  to  doubt  this. 
The  suddenness  and  rapidity  with  which  an  intense  fire  is  kin- 


424  HANDBOOK    ON    ENGINEERING. 

died  in  the  furnace,  filling  all  the  furnace  space  and  the  tubes  with 
flame,  and  with  an  intense  heat  which  envelops  all  within  the  limits 
of  draft  opening,  continuing  thus  for  a  few  minutes  only,  and  as 
suddenly  going  out,  can  hardly  be  regarded  as  the  ideal  furnace. 
Yet  there  are  thousands  of  just 'such  furnaces  at  work,  and  it  is 
altogether  probable  that  little  or  no  change  will  be  made  in  them 
by  this  class  of  manufacturers,  at  least  in  the  near  future.  In 
regard  to  the  selection  of  a  boiler  for  this  service,  we  are  brought 
back  again  to  the  question  of  hard  or  soft  water.  The  decision 
should  be  largely  influenced  by  this,  but  whatever  type  of  a  boiler 
is  selected  there  should  be  a  surplus  of  boiler  power  of  at  least  20 
per  cent,  that  is,  if  a  50  horse-power  boiler  is  needed  to  do  the 
Work,  put  in  one  of  60  horse-power;  this  will  prevent  the  fluctua- 
tions of  speed  in  the  engine  which  are  sure  to  follow  a  reduction  of 
boiler  pressure. 

This  increase  in  boiler  power  ought  not  to  be  simply  that  of 
tube  surface,  but  should  also  include  extra  water  space.  The 
reserve  power  of  a  boiler  is  in  the  water  heated  up  to  a  temperature 
corresponding  to  the  steam  pressure ;  when  this  pressure  is 
lowered,  the  water  then  gives  off  steam  corresponding  to  the  lower 
pressure ;  the  more  water  the  more  steam ;  and  in  this  way  the 
water  in  the  boiler  stores  up  heat  when  overtired,  to  give  it  off 
again  when  the  fire  is  low,  and  so  acts  a  regulator  of  pressure,  a 
thing  that  extra  tube  surface  cannot  do.  This  kind  of  firing  is 
apt  to  induce  priming,  and  for  this  reason  a  boiler  should  be 
selected  having  a  large  water  surface.  Horizontal  boilers  are,  in 
general,  to  be  preferred  over  vertical  ones  for  mills,  because  of  the 
larger  water  surface  exposed  in  proportion  to  the  heating  surface. 
If  a  tubular  boiler  is  selected,  the  water  Hue  above  the  tubes 
should  be  not  higher  than  two-thirds  the  diameter  of  the  boiler 
measured  from  the  bottom,  and  the  boiler  should  be  made  having 
the  upper  edge  of  the  top  row  of  tubes  at  least  three  inches  below 
this  ;  there  should  also  be  a  clear  space  up  through  the  center  of 


HANDBOOK    ON    ENGINEERING.  425 

the  boiler  of  sufficient  width  to  insure  a   perfect  circulation    of 
water. 

Horizontal  tubular  boilers  are  to  be  recommended  when  pure 
soft  water  is  used.  They  combine  at  once  the  qualities  of  great 
strength  without  excessive  bracing,  large  heating  surface,  high 
evaporative  capacity  without  liability  to  priming,  and  are  conve- 
nient of  access  for  external  and  internal  examination  when  set  in 
the  furnace. 

Fire  box  boilers,  or  locomotive  boilers,  as  they  are  commonly 
called,  are  best  adapted  for  small  powers  and  with  a  fuel  which 
deposits  but  little  soot  in  the  tubes.  This  kind  of  boiler  is  sup- 
plied with  portable  or  agricultural  engines  and  is  very  well  adapted 
for  that  particular  service.  In  canvassing  the  desirability  of 
this  kind  of  a  boiler  for  stationary  use,  we  must  again  refer  to  the 
kind  of  water  to  be  used  in  it.  If  the  water  is  soft  and  clean 
there  is  then  no  particular  objection  to  a  boiler  of  this  construc- 
tion being  used  for  small  powers  ;  if  the  water  is  hard  and  will 
form  scale,  it  ought  not  to  be  chosen,  but  a  flue  boiler  selected 
instead. 

Vertical  boilers  are  used  in  great  numbers  for  small  engines, 
heating,  etc.  They  have  the  merit  of  being  compact  and  low 
priced.  A  common  defect  in  the  construction  of  this  kind  of 
boiler  is  that  too  many  tubes  are  put  in  the  head  in  the  lire  box, 
thereby  preventing  a  proper  circulation  of  water  between  them. 
This  defect  in  construction  induces  priming,  with  all  its  attendant 
annoyances  and  dangers.  This  style  of  boiler  is  not  suited  to 
hard  water,  but  pure  soft  water  only.  These  boilers  should  be 
provided  with  hand  holes  above  the  crown  sheet  and  around  the 
bottom  of  the  water  legs ;  at  least  three  at  each  place  mentioned. 
In  regard  to  the  material  of  which  a  boiler  shall  be  made  there  is 
but  the  simple  choice  between  iron  and  steel. 

Steel  for  boilers  should  not  be  of  too  high  tensile  strength ;. 
55,000  to  60,000  pounds  tensile  strength  per  square  inch  makes 


426  HANDBOOK    ON    ENGINEERING . 

the  best  boilers.  If  the  steel  is  of  too  high  a  grade  it  will  take  :i 
temper,  and,  therefore,  is  utterly  unlit  for  use  in  steam  boilers  : 
if  the  steel  is  of  too  low  tensile  strength  it  is  apt  to  be  loose  or 
spongy.  Among  the  advantages  steel  possesses  over  iron  may  be 
mentioned  the  circumstance  that  it  is  a  practically  homogeneous 
material  when  properly  made  and  rolled,  consequently,  it  is  nearly 
as  strong  in  one  direction  as  it  is  in  another.  In  this  respect, 
steel  is  superior  to  iron  plate  of  equal  thickness,  because  the  latter 
is  made  up  of  several  pieces  of  iron  welded  together  and  in  rolling 
into  the  plate  it  becomes  fibrous,  and  thus  of  unequal  strength, 
being  greatest  in  the  direction  of  the  liber,  and  least,  when  tested 
across  it. 

BOILER  TRIMMINGS. 

The  common  trimmings  to  a  steam  boiler  are  a  safety  valve, 
feed  and  blow-off  pipe,  steam  pipe,  gauge  cocks,  glass  water  gauge 
and  steam  gauge ;  to  which  may  be  added  a  steam  drum  or  dome 
and  a  mud  drum.  There  are  numerous  other  devices  which  are 
attached  to  boilers  such  as  safety  gauges,  alarms,  fusible  plugs, 
automatic  dampers,  etc.  ;  many  of  these  are  very  serviceable  and 
are  well  liked  by  those  using  them. 

Safety  valves  should  always  be  large  enough  to  permit  the 
escape  of  all  the  steam  a  boiler  is  capable  of  making  and  each 
boiler  should  have  its  own  safety  valve  rather  than  connecting  two 
or  more  boilers  together,  and  depending  on  one  valve  for  the 
whole.  The  valve  and  seat  should  be  made  of  hard  gun  metal,  or 
any  other  composition  that  will  not  rust  and  stick  fast.  At  one 
time  it  was  quite  a  common  thing  to  see  a  brass  valve  fitted  to  a 
cast-iron  seat ;  this  is  wrong,  for  the  rusting  of  the  iron  would  lix 
the  valve  so  tightly  that  the  boiler  would  be  in  constant  danger  of 
rupture  from  over  pressure.  For  stationary  boilers  the  common 
ball  and  lever  safety  valves  are  generally  used.  For  stationary 
boilers  it  is  immaterial  whether  the  safety  valve  be  fitted  with  a 


ON    ENGINEERING.  427 

lever  and  weight,  or  whether  it  In1  fitted  with  a  spring.  The 
former  is  the  usual  manner  of  loading  a  safety  valve  and  has  but 
few  objections.  For  portable  engines  and  locomotives  safety 
valves  are  loaded  with  springs,  which  by  suitable  adjustment  may 
be  made  to  blow  off  at  any  desired  pressure. 

The  following1  rule  is  that  enforced  by  the  U.  S.  Government 
in  fixing  the  area  of  satetv  valves  for  ocean  and  river  service,  when 
the  ordinary  lever  and  weight  safety  valve  is  employed  :  — 

Rule* — When  the  common  safety  valve  is  employed  it  shall 
have  an  area  of  not  less  than  one  square  inch  for  each  two  square 
feet  of  grate  surface. 

Another  rule  is  to  multiply  the  pounds  of  coal  burned  per 
hour  by  4  ;  this  product  is  to  be  divided  by  the  steam  pressure, 
to  which  a  constant  number  10  is  added. 

KXAMPLK:  What  would  be  the  proper  area  for  a  safety  valve 
for  a  boiler  having  a  grate  surface  5  feet  square  and  burning  12 
pounds  of  coal  per  hour  per  square  foot  of  grate ;  the  steam 
pressure  being  75  pounds  per  square  inch? 

5x5  equal  25  square  feet  of  grate. 

25  x  12  equal  300  Ibs.  of  coal  per  hour. 

800x4  equal  1200. 

75  plus  10  equal  85  equal  steam  pressure  with  10  added,  then 
1200/85  equal  14.11  inches  area,  or  4|  inches  diameter. 

A  feed  pipe  should  be  at  least  twice  the  area  over  that  which  is 
regarded  as  simply  necessary  to  supply  the  boiler  with  water,  as 
sediment  or  scale  is  likely  to  form  in  it,  which  will  materially  re- 
duce its  area.  In  localities  where  the  water  is  hard  the  feed 
pipes  should  be  disconnected  near  the  boiler  and  examined  occa- 
sionally to  ascertain  whether  or  not  scale  is  forming  in  them. 

In  general,  the  sizes  of  feed  pipes  leading  from  the  pump 
to  the  boiler  are  fixed  by  the  size  of  tap  used  by  the  maker  of 
the  pump.  It  is  not  well  to  reduce  the  diameter  of  the  pipe  and 
the  size  should  be  the  same  throughout.  Care  should  be  exer- 


428  HANDBOOK    ON    ENGINEERING. 

cised  iii  putting  pipes  in  place  that  no  strain  be  brought  upon  them 
by  imperfect  fitting,  as  it  is  certain  to  lead  to  leaky  joints  at  some 
time  or  other.  It  is  also  desirable  that  the  pipes  be  as  short  and 
straight  as  possible.  Feed  pipes  should  never  be  placed  under 
ground  if  it  is  possible  to  make  any  different  disposition  of  them. 
In  locating  pipes  it  is  desirable  to  arrange  for  the  expansion  of 
the  boiler,  as  well  as  for  that  of  the  pipes  themselves.  In  select- 
ing a  pump  it  should  have  a  much  larger  capacity  than  that  needed 
to  supply  the  boiler,  as  there  are  many  things  which  affect  the 
working  of  a  pump,  such  as  a  defective  suction  pipe,  leaky  valves, 
etc.  It  is  the  practice  of  most  manufacturers  to  give  the  capacity 
of  their  pumps  in  gallons  of  water  delivered  per  minute,  from 
which  it  is  easy  to  select  a  suitable  size  ;  but  the  speed  given  in 
the  tables  at  which  the  pump  is  to  run  is  generally  faster  than 
that  which  it  is  desirable  to  run  them.  As  a  general  thing,  and 
without  referring  to  any  particular  maker  or  design,  it  is  a  good 
plan  to  select  a  pump  having  four  times  the  capacity  actually 
needed  for  the  boiler ;  then  the  speed  may  be  reduced  to  half  that 
given  in  the  table,  and  will  require  less  repairs,  and  will  be  a  more 
satisfactory  purchase  in  the  long  run. 

In  selecting  an  injector  or  inspirator,  the  size  should  not 
greatly  exceed  that  actually  required  to  supply  the  boiler.  In 
making  the  steam  connections  the  pipes  should  start  from  the 
steam  space  of  the  boiler  and  should  not  be  branches  merely  from 
the  other  steam  pipes ;  neither  should  the  diameters  of  the  pipes 
be  less  than  that  which  the  instrument  calls  for.  The  pipes 
should  be  as  short  and  straight  as  practicable ;  abrupt  bends 
should  always  be  avoided  in  the  suction  pipes.  If  the  water  is 
taken  from  a  place  in  which  there  are  floating  particles  of  wood, 
leaves,  etc.,  a  strainer  should  be  used;  a  large  sheet  metal  box 
with  perforated  sides,  makes  a  good  strainer ;  the  openings  ought 
not  too  greatly  exceed  an  eighth  of  an  inch  in  diameter,  and  should 
be  several  times  the  area  of  the  suction  pipe. 


HANDBOOK    ON    ENGINEERING.  429 

A  check  valve  -should  bo  fitted  with  a  valve  between  it  and  the 
boiler,  so  that  in  the  event  of  its  not  working  satisfactorily  it  may 
be  taken  apart,  cleaned  and  replaced  without  stopping  for  exami- 
nation or  repairs. 

The  blow-off  pipe  should  be  so  arranged  that  it  will  entirely 
drain  the  boiler  of  water ;  it  is  also  a  good  plan  to  set  a  boiler 
with  a  slight  inclination  toward  the  blow-off  pipe  that  it  may  be 
thoroughly  drained ;  an  inclination  of  two  inches  in  twenty  feet 
works  well  in  practice.  The  blow-off  pipe  is  usually  fitted  at  the 
back  end  of  the  boiler. 

The  steam  pipe  may  be  connected  at  any  convenient  point  on 
the  top  of  the  boiler.  If  the  boiler  is  to  furnish  steam  for  an 
engine  only,  the  common  practice  is  to  make  the  diameter  of  the 
pipe  one-fourth  that  of  the  cylinder.  The  steam  pipe  should  be 
as  short  and  straight  as  possible.  If  bends  are  to  be  introduced 
in  steam  pipes  it  is  better  to  have  a  long  curved  bend  than  the 
abrupt  right-angle  fitting  usually  employed  for  the  purpose.  It 
is  also  a  good  plan  to  provide  a  stop-valve  r  .xt  to  the  boiler  to 
shut  off  the  steam  and  prevent  it  condensir^-  in  the  steam  pipe  at 
night,  or  other  long  stoppages. 

The  gauge  cocks  should  not  be  less  than  three  in  number,  and 
may  be  of  any  of  the  various  kinds  now  in  the  market.  For 
stationary  boilers,  the  Mississippi  gauge  cock  is,  perhaps,  as 
good  as  any.  For  portable  engines  a  compression  gauge-cock  is, 
perhaps,  the  best.  The  lower  gauge-cock  should  be  at  least 
2"  above  the  tubes  or  crown  sheet,  the  middle  2"  above  the  first 
ordinary  water  line,  the  upper  2"  above  the  2  on  2"  to  3",  de- 
peudhig  on  the  size  of  the  boiler. 

A  glass  water  gauge  should  be  provided  for  each  boiler  and 
should  be  so  located  that  the  water  level  in  the  boiler  when  at  the 
lower  end  of  glass  shall  be  one  inch  above  the  top  of  flue.  When 
glass  gauges  are  so  fitted  the  fireman  can  always  tell  at  a  glance, 
just  how  much  water  he  has  above  the  flues  or  crown  sheet ;  it 


430  HANDBOOK    ON    ENGINEERING. 

also  permits  the  easy  test  of  accuracy  by  try  ing  the  gauge-cocks 
witli  the  water  at  a  certain  known  level.  Too  much  dependence 
•must  not  be  placed  on  the  glass  water-gauge  alone,  hut  should  he 
used  in  connection  with  the  gauge-cocks. 

A  steam  gauge  is  a  very  important  appendage  to  a  steam 
boiler,  and  should  be  chosen  with  special  reference  to  accuracy 
and  durability.  The  ordinary  gauges  now  in  the  market  are  the 
bent  tube  and  the  diaphragm  gauges.  It  matters  little  which  of 
the  two  kinds  is  selected,  provided  it  is  a  good  and  first-class 
gauge.  A  steam  gauge  should  be  compared  with  a  standard  test 
gauge  at  least  once  a  year,  to  see  that  it  is  correct.  The 
importance  of  this  will  be  fully  apparent  when  it  is  known  that  it 
furnishes  the  only  means  by  which  the  fireman  is  to  judge  of  the 
steam  pressure  in  the  boiler.  A  siphon  should  be  attached  to 
every  gauge,  and  provision  should  also  be  made  for  draining  the 
gauge  or  siphon,  to  prevent  freezing  when  steam  is  off  the  boiler. 
Neglect  of  this  may  endanger  the  accurate  reading  of  the  steam 
gauge  and  render  it  useless. 

Steam  dome*  —  This  is  a  reservoir  for  steam  riveted  to  the 
upper  portion  of  the  shell  and  communicated  by  a  central  opening 
with  the  steam  space  in  the  boiler.  When  this  reservoir  forms  a 
separate  fixture  and  is  attached  to  the  boiler  by  cast  or  wrought 
iron  nozzles,  it  is  then  called  a  steam  dram.  The  latter  answers 
all  the  purposes  for  stationary  boilers  that  the  former  does,  and 
is  to  be  preferred  because  of  the  smaller  openings  in  the  shell  of 
the  boiler.  A  considerable  number  of  boiler  explosions  have 
been  traced  directly  to  the  weakness  of  the  shell,  caused  by  the 
large  opening  in  and  imperfect  staying  of  the  shell  underneath 
the  dome.  When  a  dome  is  employed  and  has  a  large  hole  under- 
neath, the  strength  of  the  shell  is  impaired  in  two  ways:  1.  By 
reducing  the  longitudinal  sectional  area  of  shell  through  the  cen- 
ter of  opening  cut  for  it,  which  weakness  cannot  wholly  be  made 
good  by  a  strengthening  ring  around  the  opening.  2.  By  causing 


HANDBOOK    ON    ENGINEERING.  431 

a  tension  equal  to  that  on  the  crown  area  of  steam  dome,  upon 
the  annular  part  of  the  shell  covered  by  the  llange  of  the  dome. 
The  weakest  part  of  the  boiler  shell  will  be  where  the  distance 
from  rivet  hole  at  the  base  of  the  dome  to  edge  of  plate  is  least. 
It  is  difficult,  owing  to  the  complex  nature  of  the  strains,  to  form 
a  rule  whereby  to  determine  how  much  the  strength  of  the  shell 
is  impaired  by  using  a  dome ;  but  it  is  quite  apparent  from  gen- 
eral experience  that  they  are  in  many  cases  a  source  of  weakness, 
and  the  larger  the  dome  connection  with  the  shell,  the  greater  the 
liability  to  rupture.  This  tendency  to  rupture  is  due  to  the  fact 
that  the  dome,  with  its  connecting  flange,  is  practically  inelastic ; 
that  portion  of  the  shell  of  the  boiler  covered  by  the  dome  is,  as 
soon  as  the  pressure  is  introduced  on  both  sides  of  the  plate, 
simply  a  curved  brace.  The  pressure  of  the  steam  in  the  boiler 
has  a  tendency  to  straighten  the  shell  under  the  dome  and  thus 
brings  about  a  series  of  complex  strains  which  are  not  easily  rem- 
edied by  any  system  of  bracing,  so  that  on  the  whole  it  is  prefer- 
able to  use  a  small  connecting  nozzle  with  a  drum  above  it,  rather 
than  to  rivet  a  large  dome  directly  to  the  shell. 

Dry  pipe*  — -  This  is  a  pipe  having  numerous  small  perforations 
on  its  upper  side,  and  inserted  in  "the  upper  part  of  the  steam  space 
of  the  boiler.  This  pipe  does  not  dry  the  steam,  but  acts 
mechanically  by  separating  the  steam  from  the  wetter  when  the 
latter  is  in  a  violent  state  of  agitation,  and  is  liable  to  be  carried 
in  bulk  toward  or  into  the  steam  pipe.  The  object  of  these  numer- 
ous small  holes  in  the  pipe  is  that  a  small  quantity  of  steam  may 
be  taken  from  a  large  number  of  openings  at  one  time,  and  thus 
carried  over  a  larger  extent  of  surface  than  that  afforded  by  a 
single  opening,  and  by  this  single  device  checking  the  tendency  to 
priming. 

Steam  boiler  furnaces  are  receiving  more  attention  now  than 
perhaps  ever  before.  The  question  of  economy  of  fuel  is  being 
closely  studied,  and  there  is  now  an  effort  to  save  much  of  the 


432  HANDBOOK    ON    ENGINEERING. 

heat  which  had  formerly  been  allowed  to  go  to  waste.  The  main 
thing  in  furnace  construction  is  to  get  perfect  combustion.  With- 
out this  there  must  be  of  necessity  a  great  loss  constantly  going 
on.  There  are  some  losses  which  it  is  difficult  to  prevent,  for 
example  —  the  loss  by  the  admission  of  too  much  air  in  the  ash 
pit ;  the  loss  by  incomplete  combustion ;  the  loss  occasioned  by 
the  heated  gases  escaping  up  the  chimney ;  the  loss  by  radia- 
tion ;  but,  chief  among  these,  is  that  of  incomplete  combustion. 
To  burn  a  pound  of  coal  requires  about  twenty-four  pounds  of  air, 
or,  say  300  cubic  feet.  Most  boiler  settings  permit  from  200  to  300 
feet  to  pass  through  the  fire.  It  is  needless  to  point  out  the 
great  source  of  loss  arising  from  this  one  cause  alone.  This  may 
be  prevented  in  a  measure  by  having  a  suitable  damper  in  the 
chimney,  and  regulating  the  flow  of  escaping  gases  by  it,  instead 
of  the  ash  pit  doors.  If  the  furnace  is  so  constructed  that  the 
fuel  is  imperfectly  burned,  so  that  carbonic  oxide  instead  of  car- 
bonic acid  gas  is  formed,  the  loss  is  very  great.  This  results 
often  from  too  little  air  supply  and  too  low  temperature  in  the 
furnace.  The  furnace  doors  should  be  provided  with  an  opening 
leading  into  the  space  between  the  door  proper  and  the  liner ; 
this  opening  ought  to  have  a  sliding  or  revolving  register  by  which 
the  admission  of  air  may  be  controlled.  By  this  means,  the 
quantity  of  air  admitted  above  the  fire  may  be  adjusted  to  its 
needs  by  a  little  attention  on  the  part  of  the  fireman.  The  liner 
to  the  furnace  door  should  have  a  number  of  small  holes  in  it, 
rather  than  a  solid  plate,  with  a  space  around  the  edges.  Great 
care  should  be  exercised  in  the  construction  of  furnace  walls, 
that  the  materials  and  workmanship  be  good  throughout.  The 
entire  structure  should  be  brick.  The  outer  walls  may  be  of 
good  hard  red  brick,  but  the  interior  walls,  around  the  furnace 
and  bridge  wall,  should  be  of  fire  brick.  The  best  quality  of  fire 
brick  for  withstanding  an  intense  heat  are  very,  very  strong  and 
tenacious ;  the  structure  is  open  and  they  are  free  from  black 


HANDBOOK    ON    ENGINEERING.  433 

srx)ts,  due  to  sulphuret  of  iron  in  the  clay ;  if  well  burned  they 
will  not  be  very  light  colored  on  the  outside,  and  will  have  a 
clear  ring  when  struck. 

Fire  brick  should  be  dipped  in  a  thin  mortar  made  of  tire  clay, 
rather  than  in  a  lime  and  sand  mortar,  such  as  is  used  in  ordinary 
red  brickwork.  Inlaying  up  these  portions  of  a  boiler  furnace 
requiring  fire  brick,  provision  should  be  made  in  the  original  wall 
for  leplaciug  the*  fire  brick  and  without  disturbing  the  outer 
brickwork. 

CARE  AND  MANAGEMENT  OF  A  BOILER. 

It  is  not  enough  that  a  boiler  be  of  approved  design,  made  of 
the  best  materials,  and  put  together  in  the  best  manner ;  that  it 
have  the  best  furnace  and  the  most  approved  feed  and  safety 
apparatus.  These  are  all  desirable,  and  are  to  be  commended, 
but  cleanliness  and  careful  management  are  quite  essential  to  get- 
ting high  results,  and  are  also  conducive  to  long  use  in  service. 

Pumps*  —  Special  attention  should  be  given  at  all  times  to  the 
feed  and  safety  apparatus ;  the  pumps  should  be  in  good  working 
order ;  it  is  preferable  that  they  be  independent  steam  pumps 
rather  than  pumps  driven  by  the  engine,  or  by  a  belt ;  they  should 
be  kept  well  packed  and  the  valves  in  good  condition . 

Firing*  —  Kindle  a  fire  and  raise  steam  slowly  ;  never  force  a 
lire  so  long  as  the  water  in  the  boiler  is  below  the  boiling  point. 
The  fire  should  be  of  an  even  height,  and  of  such  a  thickness  as 
will  be  found  best  for  the  particular  fuel  to  be  burned,  but  should 
be  no  thicker  than  actually  necessary.  In  regard  to  the  size  of 
coal  used,  that  will  depend  upon  circumstances.  If  anthracite 
coal  is  used,  it  should  not,  for  stationary  boilers,  be  larger  than 
ordinary  stove  coal.  For  bituminous  coal,  which  is  always  shipped 
in  lumps  as  large  as  can  be  conveniently  handled,  the  size  will 
vary  somewhat  in  breaking,  but  it  may  in  general  be  used  in 
larger  lumps  than  anthracite.  If  the  coal  is  likely  to  cake  in  burn- 

23 


434  HANDBOOK    ON    ENGINEERING. 

ing,  the  fire  should  be  broken  up  quite  frequently  with  a  slice  biir, 
or  it  will  fuse  into  a  large  mass  in  the  center  of  the  furnace  a:id 
lower  the  rate  of  combustion.  If  the  coal  is  likely  to  form  a  con- 
siderable quantity  of  clinker,  or  enough  to  become  troublesome,  it 
may  be  advantageous  to  increase  the  grate  area  and  thus  lower 
the  rate  of  combustion  per  square  foot  of  grate,  and  have  M  Hie  of 
less  intensity.  The  lire  should  be  kept  free  from  ashes,  and  the 
ash  pit  should  be  kept  clean.  Whenever  the  fire  door  of  a  steam 
boiler  furnace  is  opened,  the  damper  should  be  closed  to  prevent 
the  sudden  reduction  of  temperature  underneath,  which  is  likely 
to  injure  the  boiler  by  contraction,  and  thus  render  it  likely  to 
spring  a  leak  around  the  riveted  joints.  Some  firemen  are  very 
careless  in  this  respect,  and  there  is  little  doubt  that  many  a  dis- 
agreeable job  of  repairing  a  leaky  seam  might  be  prevented  by 
this  simple  precaution. 

Gauge  cocks  should  be  used  constantly  to  keep  them  free  from 
any  accumulation  of  sediment.  It  is  a  very  common  practice  to 
rely  wholly  on  the  indications  of  the  glass  water  gauge  for  the 
water  level  in  the  boiler.  This  is  all  wrong  and  should  be  dis- 
continued, if  once  begun.  The  glass  water  gauge  serves  a  very 
useful  purpose,  but  it  should  not  be  wholly  relied  on  in  practice. 
In  using  the  ordinary  gauge  cocks,  the  ear  more  than  the  eye, 
detects  the  water  level,  and  thus  acts  as  a  check  on  the  indications 
given  by  the  glass  gauge. 

Water  gauges  should  be  tested  several  times  during  the  day  to 
see  that  they  are  clear,  and  to  keep  them  free  from  any  sediment 
likely  to  form  around  the  lower  opening  to  the  water  in  the 
boiler.  If  this  is  not  attended  to,  the  water  gauge  is  likely  to 
indicate  a  wrong  water  level  and  a  serious  accident  may  be  the 
result. 

Steam  or  pressure  gauges  are  likely  to  become  set  after  long 
use  and  should  be  tested  at  least  once,  or  better  still,  twice  a  year 
by  a  standard  gauge  known  to  be  correct.  They  should  also  be 


HANDBOOK    ON    ENGINEERING.  435 

tested  every  few  days  if  the  boilers  are  constantly  under  steam 
by  turning  off  the  steam  and  allowing  the  pointer  to  run  back  to 
zero.  If  there  are  two  or  more  boilers  set  together  in  one  battery, 
and  each  boiler  has  its  own  steam  gauge,  and  which  will,  starting 
from  the  zero  point,  indicate  the  same  pressure  on  all  the  gauges, 
they  may  be  assumed  to  be  correct. 

Blow-off  cocks  or  valves  should  be  examined  frequently  and 
should  never  be  allowed  to  leak.  In  general  a  cock  is  to  be  pre- 
ferred to  a  valve,  but  both  is  safer  than  one ;  if  the  latter  is 
selected  it  should  be  some  one  of  the  various  ;i  straight-way 
valves,"  of  which  there  are  now  several  in  the  market.  If  the 
cock  is  a  large  one,  and  especially  if  it  has  either  a  cast  iron  shell 
or  plug,  it  should  be  taken  apart  after  each  cleaning  out  of  the 
boilers,  examined,  greased  with  tallow  and  returned. 

Blowing1  out*  —  This  should  be  done  at  least  once  a  day, 
except  in  the  very  rare  instances  in  which  water  is  used  that  will 
not  form  a  scale.  The  water  should  not  be  let  out  of  a  boiler  or 
boilers  until  the  furnace  is  quite  cold,  as  the  heat  retained  in  the 
walls  is  likely  to  injure  an  empty  boiler  directly  by  overheating 
the  plates,  and  indirectly  by  hardening  the  scale  within  the 
boiler.  Bad  effects  are  likely  to  follow  when  a  boiler  is  emptied 
of  its  water  before  the  side  walls  have  become  cool ;  but  greater 
injury  is  likely  to  result  when  cold  water  is  pumped  into  an  empty 
boiler  heated  in  this  manner.  The  unequal  contraction  of  the 
boiler  is  likely  to  produce  leaky  seams  in  the  shell  and  to  loosen 
the  tubes  and  stays.  It  is  a  better  plan  to  allow  the  boiler  to 
remain  empty  until  it  is  quite  cold,  or  sufficiently  reduced  in  tem- 
perature to  permit  its  being  filled  without  injury.  Many  boilers 
of  good  material  and  workmanship  have  been  ruined  by  the 
neglect  of  this  simple  precaution. 

Fusible  plugs  should  be  carefully  examined  every  six  months, 
as  scale  is  likely  to  form  over  the  portion  projecting  into  the 
water  space.  It  is  only  a  question  of  time  when  this  scale 


436  HANDBOOK    ON    ENGINEERING. 

would  form  over  the  end  of  the  plug,  and  thick  enough  to  with- 
stand the  pressure  of  steam  and  thus  fail  in  the  accomplishment  of 
the  very  object  for  which  it  was  introduced.  This  applies  espe- 
cially to  the  fusible  plugs  inserted  in  the  crown  sheets  of  portable 
engine  boilers. 

Cleaning  tubes*  —  This  should  be  done  every  day  if  bitumin- 
ous coal  is  used.  A  portable  steam  jet  will  be  found  an  extremely 
useful  contrivance  which  will  keep  them  reasonably  clean  by  blow- 
ing out  the  loose  soot  and  ashes  deposited  in  the  tubes.  Every 
two  or  three  days,  or  at  least  once  a  week,  a  tube  scraper  or  stiff 
brush  should  be  used  to  take  out  all  the  ashes  or  soot  adhering 
to  the  tubes  and  which  cannot  be  blown  out  with  the  jet.  Flues 
may  be  cleaned  the  same  way  but  will  not  require  to  be  done  so 
frequently. 

Low  water*  —  If  from  any  cause  the  water  gets  low  in  the 
boiler,  bank  the  fire  with  ashes  or  with  fresh  coal  as  quickly  as 
possible,  shut  the  damper  and  ash  pit  doors  and  leave  the  fire 
doors  wide  open ;  do  not  disturb  the  running  of  the  engine  but 
allow  it  to  use  all  the  steam  the  boiler  is  making ;  do  not 
under  any  circumstances  attempt  to  force  water  in  the  boiler. 
After  the  steam  is  all  used  and  the  boiler  cooled  sufficiently  to  be 
safe,  then  the  water  may  be  admitted  and  brought  up  to  the  reg- 
ular working  height ;  the  damper  opened  and  the  fires  allowed  to 
burn  and  stearn  raised  as  usual ;  provided,  no  injury  has  been 
done  the  boiler  by  overheating. 

Foaming  and  priming  are  always  troublesome  and  often  danger- 
ous. Some  boilers  prime  almost  constantly,  because  of  their  bad 
proportion,  and  will  require  the  constant  care  of  the  person  in 
charge,  especially  at  such  times  as  the  engine  may  be  using  the 
steam  up  to  the  full  capacity  of  the  boiler.  In  a  case  of  this  kind, 
an  increase  in  pressure  will  often  check,  but  will  not  entirely 
prevent  it ;  nothing  short  of  an  increase  of  water  surface,  or  a 
better  circulation  of  water,  or  a  larger  steam  room  will  afford  a 


HANDBOOK   ON   ENGINEERING.  437 

complete  remedy.  If  the  foaming  or  priming  is  due  to  a  sudden 
liberation  of  steam,  or  on  account  of  impure  feed  water  it  may  be 
checked  by  closing  the  throttle  valve  to  the  engine  and  opening 
he  lire  door  for  a  few  minutes.  The  surface  blow  may  be  used 
with  advantage  at  this  time,  by  blowing  off  the  impurities  collected 
on  the  surface  of  the  water.  The  feed  pump  may  be  used  if 
necessary,  but  care  should  be  exercised  that  too  much  cold  water 
be  not  forced  into  the  boiler,  and  thus  lose  time  by  having  to 
wait  for  the  accumulation  of  the  regular  steam  pressure  required 
for  the  engine.  The  dangers  attending  foaming  or  priming  are  r. 
the  laying  bare  of  heating  surfaces  in  the  boiler,  and  of  breaking 
down  the  engine  by  working  water  into  the  cylinder.  The  com- 
monest damage  to  the  engine  being  either  the  breaking  of  a  cylin- 
der head,  or  the  cross-head,  or  the  breaking  of  the  piston.  Wbeu 
boilers  are  new  and  set  to  work  for  the  first  time  priming  is  a  very 
frequent  occurrence  ;  in  fact,  it  may  be  said  that  for  the  first  few 
days  there  is  always  more  or  less  of  it.  All  that  is  needed  during 
this  time  is  a  little  care  on  the  part  of  the  attendant  to  see  that 
the  water  is  kept  up  to  the  require^  level  in  the  boiler ;  it  is  also 
recommended  that  the  throttle  valve  to  the  engine  be  partially 
closed  to  prevent  any  very  great  variation  of  pressure  in  the 
boiler,  and  thus  prevent  water  passing  over  with  the  steam 
in  such  quantities  as  to  become  dangerous.  If  a  boiler 
continues  to  prime  after  it  has  had  a  week's  work  and 
then  thoroughly  cleaned,  the  causes  are  to  be  attributed  to 
other  than  the  grease  and  dirt  in  it,  which  are  inseparable  from 
the  manufacture.  As  already  said,  priming  may  be  caused  by  a 
sudden  reduction  of  pressure  ;  that  is,  a  boiler  may  be  working 
smoothly  and  well  with  say  80  pounds  pressure ;  if  an  increase 
of  load  be  suddenly  applied  to  an  engine  so  as  to  reduce  the 
pressure  to  70  or  60  pounds,  this  sudden  reduction  of  pressure 
will  almost  always  cause  priming ;  the  less  the  steam  space  in  the 
boiler,  the  greater  the  tendency  to  prime,  and  the  greater  the 


438  HANDBOOK    ON    ENGINEERING. 

difficulty  in  checking  it.  The  only  permanent  cure  for  this  is 
more  boiler  power;  as  a  temporary  expedient,  the  engine  should 
be  throttled  sufficiently  to  make  the  drain  upon  the  boiler  con- 
stant instead  of  intermittent.  If  the  duty  required  of  an  engine 
is  irregular,  the  steam  pressure  should  be  carried  higher ;  in  any 
case  similar  to  the  above,  it  is  recommended  that  the  pressure  be 
increased  to  i)0  or  100  pounds  and  the  throttling  to  begin  with 
the  increased  drain  upon  the  boiler.  But  this  is  at  best  a  mere 
makeshift,  and  a  larger  boiler  power  becomes  imperative  both 
on  the  score  of  economy  and  safely. 

WATER  FOR  USE  IN  BOILERS. 

Water  is  never  pure,  except  when  made  so  in  a  laboratory  or 
by  distillation  ;  the  impurities  may  be  divided  into  four  classes : 
1.  Mechanical  impurities.  2.  Gaseous  impurities.  3.  Dissolved 
mineral  impurities.  4.  Organic  impurities. 

(a)  Mechanical  impurities  may  be    both  mineral  and  organic. 
The  commonest  suspended   impurity  in  water  is  mud  or  sand ; 
these  may  be  removed    by  filtration  or  by  allowing  the  water  to 
stand  long  enough  to  let  theiri  settle  to  the  bottom  of  the  tank  or 
cistern  and  then   carefully  drawing  the   water  from  the  top,  and 
without  disturbing  the  bottom. 

(b)  Gaseous  impurities  in  water  vary  somewhat  according  to  the 
localities  from  which  they  are  obtained.     The  commonest  gases 
found  in  the  water  are  an  excess  of  oxygen,  nitrogen  and  carbonic 
acid.     These  have  no  effect  on  water  intended  for  steam  boilers. 

(c)  Dissolved    mineral    impurities  in    water    are  of  the    most 
varied  description,  and  are  almost  always  found  in  it.     Among 
these  are  found  salts  of  iron,  sulphate  and  carbonates  of  lime; 
sulphate  and  carbonates  of  magnesia ;   salt  and  alkalies,  such  as 
soda,   potash,    etc.  ;   acids,   such    as    sulphuric,  phosphoric,  and 
others.     All  of  these  are  more  or  less  injurious  to  steam  boilers. 
The  most  objectionable  are  the  salts  of  lime  and  magnesia,  which 
impart  to  water  that  property  known    as  hardness.     When  such 


HANDBOOK    ON    ENGINEERING.  4? 9 

water  is  used  in  a  steam  boiler  a  scale  will  gradually  form,  which 
will,  in  a  short  time,  become  very  troublesome. 

(d)  Organic  impurities  are  present,  to  a  certain  extent,  in 
most  waters.  They  are  sometimes  present  in  the  water  in  suffi- 
cient quantities  to  give  it  a  very  decided  color  and  taste. 

The  presence  of  organic  matter  in  wa,ter  is  often  dangerous  to 
health,  and  maybe  a  means  of  spreading  contagious  diseases, 
but  has  little  or  no  bad  effect  yi  any  water  used  for  steam  boilers. 
In  general,  water  is  regarded  by  engineers  as  being  either  soft, 
hard  or  salt. 

Ebullition*  —  Is  the  motion  produced  in  a  liquid  by  its  rapid 
conversion  into  vapor.  When  heat  is  applied  to  the  bottom  of  a 
boiler,  the  particles  of  water  in  contact  with  the  plates  become 
heated  and  immediately  expand,  and  becoming  specifically  lighter, 
pass  upwards  through  the  colder  body  of  water  above  ;  the  heat  of 
the  furnace  is  in  this  way  diffused  throughout  the  Avhole  body  of 
water  in  the  boiler  by  a  translation  of  the  particles  of  water  from 
below  upwards,  and  from  top  to  bottom  in  regular  succession. 
After  a  time  this  liquid  mass  becomes  heated  to  a  degree  in  which 
there  is  a  violent  agitation  of  the  whole  body  of  water,  steam  is 
given  off  and  it  is  said  to  boil.  The  temperature  at  the  boiling 
point  of  water,  at  ordinary  atmospheric  pressure,  is  212°  Fahr., 
and  increases  as  the  pressure  of  steam  above  it  increases. 

Distilled  water  for  boilers  i«  not  to  be  recommended  without 
some  reservation.  Chemically  pure  water,  and  especially  water 
which  has  I  teen  redistilled  several  times,  has  a  corrosive  action  on 
iron  which  is  often  very  troublesome.  The  effect  on  steel  plates 
by  the  use  of  water  several  times  redistilled,  such,  for  example,  as 
that  supplied  for  heating  buildings,  is  well  known  ;  information  is 
yet  wanting  which  shall  point  with  certainty  to  the  exact  change 
which  the  water  undergoes  and  explain  why  its  action  on  or 
affinity  for  steel  is  so  greatly  intensified.  It  has  been  suggested 
as  a  means  of  neutralizing  this  corrosive  action  of  the  water,  to 


440  HANDBOOK    ON    ENGINEERING. 

introduce  with  the  feed  other  water,  which  shall  have  the  prop- 
erty of  forming  a  scale  and  continuing  it  long  enough  and  at  such 
intervals  as  will  permit  the  formation  of  a  thin  scale  in  the  interior 
of  the  boiler.  However  objectionable  this  may  seem  at  first 
sight,  it  is  at  present  the  best  practical  solution  of  the  difficulty. 

Scale  is  a  bad  conductor  of  heat  and  is  opposed  to  economical 
evaporation.  It  is  estimated  that  a  thickness  of  half  an  inch  of 
hard  scale  firmly  attached  to  a  boiler  plate  will  require  a  temper- 
ature of  about  700°  Fahr.  in  the  boiler  plate  in  order  to  raise  and 
maintain  an  ordinary  steam  pressure  of  75  pounds.  The  mis- 
chievous effects  of  accumulated  scale  in  the  boiler,  especially  in 
the  plates  immediately  over  the  fire,  are :  (1)  preventing  the  water 
from  coming  in  contact  with  the  plates,  and  thus  directly  con- 
tributing to  the  overheating  of  the  latter;  and  (2)  by  causing  a 
change  of  structure  in  the  plates  and  the  consequent  weakening 
brought  about  by  this  continual  overheating,  which  would,  in  a 
short  time,  render  an  iron  or  a  steel  plate  wholly  unfit  for  use  in 
a  steam  boiler.  The  two  principal  ingredients  in  boiler  scale  are 
lime  and  magnesia.  The  lime,  when  in  combination  with 
carbonic  acid,  forms  carbonate  of  lime  ;  when  in  combination  with 
sulphuric  acid,  it  then  becomes  sulphate  of  lime.  This  is  also 
true  of  magnesia. 

Carbonate  of  lime  will  form  in  the  boiler  as  a  loose  powder 
which  is  held  mechanically  in  suspenion ;  while  in  this  stage  it 
may  be  blown  out  of  the  boiler  without  injury  to  it ;  but  it  is 
seldom  that  a  pure  carbonate  is  formed  in  the  boiler  as  there  are 
other  impurities  in  the  water  with  which  it  combines  to  form  a 
hard  scale.  This  is  especially  true  in  such  waters  as  also  contain 
sulphate  of  lime  in  solution.  This  fine  powder  (carbonate  of 
lime),  will  form  a  hard  scale  should  any  adhere  to  tHe  sides  or 
bottom  of  a  boiler ;  in  any  case  where  the  boiler  is  blown  out  dry 
while  the  furnace  walls  are  still  hot;  and  this,  in  itself,  forms  an 
excellent  reason  why  boilers  should  stand  until  the  furnace  walls 


HANDBOOK    ON    ENGINEERING.  441 

are  cold  before  blowing  out.  When  emptied,  nearly  or  all  of  this 
slushy  deposit  may  be  washed  out  of  the  boiler  by  means  of  a 
hose. 

Sulphate  of  lime  is  not  so  easily  got  rid  of,  as  it  is]heavier  than 
carbonate  of  lime  and  adheres  to  the  plates  while  the  boiler  is  at 
work.  It  is  the  most  troublesome  scale  steam  engineers  have  to 
deal  with  ;  it  is  very  difficult  to  remove  and  by  successive  layers 
becomes  dangerous,  on  account  of  the  thickness  to  which  it 
eventually  accumulates. 

The  carbonates  of  lime  and  magnesia  may  be  largely  arrested 
by  passing  the  feed  water  through  a  suitable  heater  and  lime 
extractor.  It  must  be  apparent  to  every  one  that  any  device 
which  will  accomplish  this  is  a  very  desirable  attachment  to  a 
steam  boiler.  As  it  is  not  possible  to  eliminate  all  the  foreign 
matter  in  the  water  from  it,  recourse  is  often  had  to  the  use  of 
solvents  and  chemical  agencies  for  the  prevention  of  scale.  Some 
of  these  are  very  simple  and  within  easy  reach ;  others  are  sur- 
rounded by  an  atmosphere  of  uncertainty  and  the  real  nature  of 
the  compound  is  hidden  under  a  meaningless  trade-mark.  For 
carbonate  of  lime,  potatoes  have  been  found  to  be  very  service- 
able in  preventing  the  formation  of  scale ;  its  action  appears  to 
be  that  of  surrounding  the  particles  of  lime  with  a  coating  of 
starch  and  gelatine,  and  thus  preventing  the  cohesion  of  these 
particles  to  form  a  mass.  Various  astringents  have  been  used  for 
this  purpose,  such  as  extracts  of  oak  and  hemlock  bark,  nutgalls, 
catechu,  etc.,  with  varying  success. 

Carbonate  of  soda  has  been  used  and  with  very  great  success  in 
some  localities,  not  only  in  preventing,  but  in  actually  removing 
scale  already  formed.  It  acts  on  carbonate  of  lime  not  only,  but 
on  the  sulphate  afso.  It  is  clean,  free  from  grit,  and  is  quite 
unobjectionable  in  the  boiler ;  one  or  more  pounds  per  day,  de- 
pending on  the  size  of  the  boiler,  may  be  admitted  through  the 
pump  with  the  feed  water ;  or  admitted  in  the  morning  before 


442  HANDBOOK    ON    ENCUXKKKING. 

firing  up,  by  simply  mixing  with  water  and  pouring  into  the  boiler- 
through  the  safety  valve  or  other  opening. 

Tannate  of  soda  has  been  similarly  employed  and  is  an  excel- 
lent scale  preventive.  It  will  also  act  as  a  solvent  for  scale 
already  formed  in  the  boiler,  acting  on  sulphate  as  well  as  carbon- 
ate of  lime. 

Crude  petroleum  has  been  found  very  beneficial  in  removing 
the  hard  scale  composed  principally  of  sulphate  of  lime. 

Zinc  in  steam  boilers.  —  The  employment  of  zinc  in  steam 
boilers,  like  that  of  soda,  has  been  adopted  for  two  distinct 
objects:  (1)  to  prevent  corrosion,  and  (2)  to  prevent  and 
remove  incrustation.  To  attain  the  first  object,  it  has  been  used 
chiefly  in  marine  boilers,  and  for  the  second,  chiefly  in  boilers  fed 
with  fresh  water.  In  order  that  the  application  of  zinc  in  marine 
boilers  may  be  effective,  it  is  necessary  that  the  metallic  contact 
should  be  insured.  If  galvanic  action  alone  is  relied  upon  for  the 
protection  of  the  plates  and  tubes,  it  will  doubtless  be  diminished 
materially  by  the  coating  of  oxide  that  exists  between  all  joints  of 
plates,  whether  lapped  or  butted,  and  also  between  the  rivets  and 
the  plates.  Assuming  the  preservative  action  of  zinc  to  be  proved 
when  properly  applied,  we  have  now  two  systems  for  preventing 
the  internal  decay  of  marine  boilers,  viz. :  allowing  the  plates  and 
tubes  to  become  coated  with  scale,  and  employing  zinc.  It 
remains  to  decide  which  of  these  two  systems  is  the  best  with 
respect  to  economy  and  practicability. 

We  come  now  to  consider  the  use  of  zinc  for  preventing  and 
removing  incrustation. 

At  one  time  it  was  considered  that  the  action  of  zinc  in  pre- 
venting incrustation  was  physical  or  mechanical.  The  particles 
of  zinc,  as  it  wasted  away,  were  supposed  to  become  mixed 
amongst  the  solid  matter  precipitated  from  the  water,  in  such  a 
manner  as  to  prevent  it  adhering  together,  so  as  to  form  a  hard 
scale  ;  or  the  particles  of  zinc  were  supposed  to  become  deposited 


HANDBOOK    ON    ENGINEERING.  .      443 

upon  the  plates,  and  so  prevent  the  scale  from  adhering  to  them* 
Then  it  was  suggested  that  the  zinc  acted  chemically,  and  now,  it 
is  the  generally  received  opinion  that  its  action  is  galvanic  in 
preventing  incrustation  as  well  as  in  preventing  corrosion.  When 
the  water  contains  an  excess  of  sulphates  or  chlorides  over  the 
carbonates,  the  acid  of  the  former  will  form  soluble  salts  with  the 
oxide  of  zinc,  the  surface  of  the  zinc  will  be  kept  clean,  and  the 
galvanic  current,  to  which  the  efficiency  of  the  zinc  is  due,  will  be 
maintained.  On  the  other  hand,  should  there  be  a  preponderat- 
ing amount  of  carbonates,  the  zinc  will  be  covered  first  with  oxide, 
then  with  carbonates  and  its  useful  action  arrested  and  stopped. 
It  is  quite  as  important  that  the  zinc  should  be  in  metallic  con- 
tact with  the  plates  when  used  to  prevent  incrustation,  as  when 
employed  to  prevent  corrosion.  The  application  of  zinc  for  the 
former  purpose  should  never  be  attempted  without  first  having  the 
water  analyzed  in  order  to  ascertain  whether  it  is  likely  to  be 
effective.  The  use  of  zinc  in  externally  fired  boilers  should  be 
attempted  with  great  caution,  as  when  efficacious  in  preventing 
the  formation  of  a  hard  scale,  it  is  liable  to  produce  a  heavy 
sludge  that  may  settle  over  the  furnace  plates  and  lead  to  over- 
heating. On  the  whole  we  cannot  but  regard  the  evidence  as  to 
the  effect  of  zinc  upon  incrustation  as  being  very  conflicting. 

Leaks  should  be  stopped  as  soon  as  possible  after  their  dis- 
covery ;  the  kind  of  leak  will  indicate  the  treatment  necessary. 
If  it  occurs  around  the  ends  of  the  tubes,  it  may  be  stopped  by 
expanding  the  tubes  anew ;  if  in  a  riveted  joint,  it  should  be  care- 
fully examined,  especially  along  the  line  of  the  rivets  and  care 
should  be  exercised  in  determining  whether  there  is  a  crack 
extending  from  rivet  to  rivet  along  the  line  of  the  holes ;  should 
this  prove  to  be  the  case,  the  boiler  is  then  in  an  extremely 
dangerous  condition  and  under  no  circumstances  should  it  be 
again  fired  up  until  suitable  repairs  have  been  made  which  will 
in  sure  its  safety. 


444  HANDBOOK    ON    ENGINEERING. 

Blisters  occur  in  plates  which  are  made  up  of  several  thick- 
nesses of  iron  and  which  from  some  cause  were  not  thoroughly 
welded  before  the  final  rolling  into  plates.  When  such  a  plate 
comes  in  contact  with  the  heat  of  the  furnace  the  thinnest  portion 
of  the  defective  plate  "  buckles  "  and  forms  what  is  called  a 
blister.  As  soon  as  discovered,  there  should  be  thorough  exami- 
nation of  the  plate  and  if  repairs  are  needed  there  should  be  as 
little  delay  as  possible  in  making  them.  If  the  blister  be  very 
thin  and  altogether  on  the  surface  it  may  be  chipped  and  dressed 
around  the  edges ;  if  the  thickness  is  equal  or  exceeds  Jg"  the 
blister  should  be  cut  off  and  patched,  or  a  new  plate  put  in. 

Patching  boilers*  —  When  a  boiler  requires  patching  it  is  bet- 
ter to  cut  out  the  defective  sheets  and  rivet  in  a  new  one ;  or  if 
this  cannot  be  done,  a  new  piece  large  enough  to  cover  the  defect 
in  the  old  sheet  may  be  riveted  over  the  hole  from  which  the 
defective  portion  has  been  cut.  If  this  occurs  in  any  portion  of 
the  boilei  subject  to  the  action  of  tire,  the  lap  should  be  the  s-ame 
as  the  edges  of  the  boiler  seams,  and  should  be  carefully  calked 
around  the  edges  after  the  riveting.  Whenever  the  blisters  occur 
in  a  plate,  patching  is  a  comparatively  simple  thing  as  against  the 
repairs  of  a  plate  worn  by  corrosion.  In  the  latter  case,  the 
defective  portions  of  the  plate  should  be  entirely  removed  and  the 
openings  should  show  sound  metal  all  around  and  of  full  thick- 
ness. If  this  cannot  be  obtained  within  a  reasonable  sized  open- 
ing then  the  whole  plate  should  be  removed. 

It  often  occurs  that  a  minor  defect  is  found  in  a  plate  and  at  a 
time  when  it  is  not  convenient  to  stop  for  repairs;  in  such  an 
event  a  "  soft  patch  "  is  often  applied.  This  consists  of  a  piece 
of  wrought  iron  carefully  fitted  to  that  portion  of  the  boiler  plate 
needing  repairs ;  holes  are  fitted  in  both  plates  and  patch,  and 
"  patch  bolts  "  provided  for  them.  A  thick  putty  consisting  of 
white  and  red  lead  with  iron  borings  or  filings  in  them  placed 
evenly  over  the  inner  surface  of  the  patch,  which  is  then  tightly 


HANDBOOK    ON    ENGINEERING.  445 

bolted  to  the  boiler  plate.  This  is  best  but  a  temporary  make- 
shift and  ought  never  to  be  regarded  as  a  permanent  repair.  A 
mistake  is  often  made  of  making  a  patch  of  thicker  metal  than 
that  of  the  shell  of  the  boiler  needing  it.  A  moment's  reflection 
ought  to  show  the  absurdity  of  putting  on  a  T5F  or  |  patch  on  an 
old  i  inch  boiler  shell;  yet  it  is  not  so  rare  as  one  would  imagine. 
A  piece  of  new  iron  T3^"  thick  will,  in  most  cases,  be  found  to  be 
stronger  than  that  portion  of  a  J"  old  plate  needing  repairs. 

Inspection*  —  A  careful  external  and  internal  examination  of  a 
boiler  is  to  be  commended  for  many  reasons.  This  should  be  as 
frequent  as  possible  and  thoroughly  done ;  it  should  include  the 
boiler  not  only,  but  all  the  attachments  which  affect  its  working 
or  pressure.  Particular  attention  should  be  paid  to  the  examina- 
tion of  all  braces  and  stays,  safety  valve,  pressure  gauges,  water 
gauges,  feed  and  blow-off  apparatus,  etc.  ;  these  latter  refer  more 
particularly  to  constructive  details  necessary  to  proper  manage- 
ment and  safety.  The  inspection  would  obviously  be  incomplete, 
did  it  not  include  an  examination  into  the  causes  of  "  wear  and 
tear,"  and  determine  the  extent  to  which  it  had  progressed. 
Among  the  several  causes  which  directly  tend  to  rendering  a 
boiler  unsafe,  may  be  mentioned  the  dangerous  results  occasioned 
by  the  overheating  of  plates,  thus  changing  the  structure  of  the 
iron  from  fine  granular,  or  fibrous,  to  coarse  crystalline.  This 
may  easily  be  detected  by  examination,  and  will  in  general  be 
found  to  occur  in  such  cases  where  the  boilers  are  too  small  for 
the  work,  are  fired  too  hard,  or  have  a  considerable  accumulation 
of  scale  or  sediment  in  contact  with  the  plates.  Blistered  plates 
are  almost  instantly  detected  at  sight,  so  also  is  corrosion,  from 
whatever  cause  it  may  have  proceeded. 

Corrosion  of  boiler  plates*  —  Iron  will  corrode  rapidly  when 
subjected  to  the  intermittent  action  of  moisture  and  dryness. 
Land  boilers  are  less  subject  to  corrosion  than  marine  boilers. 
The  corrosion  of  a  boiler  may  be  either  external  or  internal.  Ex- 


446  HANDBOOK    ON    ENGINEERING. 

ternal  corrosion  may,  in  general,  be  easily  prevented  by  carefully 
caulking  all  leaks  in  the  boiler ;  by  preventing  the  dropping  cf 
water  on  the  plates,  such,  for  example,  as  from  a  leaky  joint  in 
the  steam  pipe  or  from  the  safety  valve.  A  leaky  roof,  by  allow- 
ing a  continual  or  occasional  dropping  of  water  on  the  top  of  a 
boiler,  especially  if  the  boiler  is  not  in  constant  use,  would  pro- 
mote external  corrosion.  Sometimes  external  corrosion  is  caused 
by  the  use  of  coal  having  sulphur  in  it,  and  acts  in  this  way :  The 
sulphur  passes  off  from  the  fire  as  sulphurous  oxide,  which  often 
attaches  to  the  sides  of  a  boiler ;  so  long  as  this  is  dry  no  especial 
mischief  is  done ;  but  if  it  comes  in  contact  with  a  wet  plate  the 
sulphurous  oxide  is  converted  into  sulphuric  acid  over  so  much 
of  the  surface  as  the  moisture  extends;  this  acid  attacks,  and 
will,  in  time,  entirely  destroy  the  boiler  plate.  Internal  corrosion 
is  not  so  easily  accounted  for  and  is  very  difficult  to  correct, 
especially  when  it  occurs  above  the  water  line.  It  is  generally 
believed  to  be  due  to  the  action  of  acids  in  the  feed  water. 
Marine  boilers  are  especially  subject  to  internal  corrosion  when 
used  in  connection  with  surface  condensers.  A  few  years  ago  it 
was  generally  supposed  to  be  due  to  galvanic  action  but  that  idea 
is  now  almost  entirely  given  up.  From  the  fact  that  boilers  using 
distilled  water  fed  into  them  from  surface  condensers  are  more 
liable  to  internal  corrosion  than  other  boilers,  has  led  to  the  theory 
that  it  is  the  pure  water  that  does  the  mischief,  and  that  a  water 
containing  in  slight  degree  a  scale-forming  salt,  is  to  be  preferred 
to  water  which  is  absolutely  pure.  Whatever  maybe  the  truth  or 
falsity  of  this  theory,  it  is  a  well  established  fact  that  distilled 
water  has  a  most  pernicious  action  on  various  metals,  especially 
on  steel,  lead  and  iron.  This  action  is  attributed  to  its  peculiar 
property,  as  compared  with  ordinary  water,  of  dissolving  free 
carbonic  acid.  One  of  the  worst  features  in  connection  with 
internal  corrosion  is  that  its  progress  cannot  be  easily  traced  on 
account  of  the  boiler  being  closed  while  at  work.  As  it  does  not 


HANDBOOK    ON    ENGINEERING.  447 

usually  extend  over  any  very  great  extent  of  surface,  the  ordinary 
hydraulic  test  fails  to  reveal  the  locality  of  corroded  spots  ;  the 
hammer  test,  on  the  contrary,  rarely  fails  to  locate  them,  if  the 
plates  are  much  thinned  by  its  action. 

Testing  boilers*  —  It  is  the  general  practice  to  apply  the 
hydraulic  test  to  all  new  steam  boilers  at  the  place  of  manufacture, 
and  before  shipment.  The  pressure  employed  in  the  test  is  from 
one  and  ti  half  to  twice  the  intended  working  steam  pressure. 
This  test  is  only  valuable  in  bringing  to  notice  defects  which 
would  escape  ordinary  inspection.  It  is  not  to  be  assumed  that 
it  in  any  way  assures  good  workmanship,  or  material,  or*  good 
design,  or  proper  proportions ;  it  simply  shows  that  the  boiler 
being  tested  is  able  to  withstand  this  -  pressure  without  leak- 
ing at  the  joints,  or  distorting  the  shell  to  an  injurious  degree. 
Bad  workmanship  may  often  be  detected  at  a  glance  by  an  expe- 
rienced person.  The  material  must N be  judged  by  the  tensile 
strength  and  ductility  of  the  sample  tested.  The  design  and  pro- 
portions are  to  be  judged  on  constructive  grounds,  and  have  little 
or  nothing  in  common  with  the  hydraulic  test.  The  great  majority 
of  buyers  of  steam  boilers  have  but  little  knowledge  on  the  sub- 
ject of  tests,  and  too  often  conclude  that  if  they  have  a  certified 
copy  of  a  record  showing  that  a  particular  boiler  withstood  a  test 
of  say,  150  Ibs.,  it  is  a  good  and  safe  boiler  at  75  to  100  Ibs. 
steam  pressure.  If  the  boiler  is  a  new  one  and  by  a  reputable 
maker,  that  may  be  true ;  if  it  has  been  used  and  put  upon  the 
market  as  a  second-hand  boiler,  it  may  be  anything  but  safe  at 
half  the  pressure  named.  By  the  hydraulic  test,  the  braces  in  a 
boiler  may  be  broken,  joints  strained  so  as  to  make  them  leak, 
bolts  or  pins  may  be  sheared  off,  or  so  distorted  as  to  be  of  little 
or  no  service  in  resisting  steam  when  pressure  is  on. 

Hammer  test.  —  The  practice  of  inspecting  boilers  by  sounding 
with  a  hammer  is,  in  many  respects,  to  be  commended.  It 
requires  some  practical  experience  in  order  to  detect  blisters  and 


448  HANDBOOK    ON    ENGINEERING. 

the  wasting  of  plates,  by  sound  alone.  The  hammer  test  is 
especially  applicable  to  the  thorough  inspection  of  old  boilers.  It 
frequently  happens  in  making  a  test  that  a  blow  of  the  hand 
hammer  will  either  distort  it,  or  be  driven  entirely  through  the 
plate ;  and  it  is  just  here  that  the  superiority  of  this  method  of 
testing  over,  or  in  connection  with  the  hydraulic  test,  becomes 
fully  apparent.  The  location  of  stays,  joints  and  boiler  fittings  all 
modify  and  are  apt  to  mislead  the  inspector  if  he  depends  upon 
sound  alone.  There  is  a  certain  spring  of  the  hammer  and  a  clear 
ring  indicative  of  sound  plates,  which  are  wanting  in  plates  much 
corroded  or  blistered.  The  presence  of  scale  on  the  inside  of  the 
boiler  has  a  modifying  action  on  the  sound  of  the  plate.  When  a 
supposed  defect  is  discovered,  a  hole  should  be  drilled  through 
the  sheet  by  which  its  thickness  may  be  determined,  as  well  as 
its  condition. 

In  order  to  thoroughly  inspect  a  boiler,  the  inspector  should 
crawl  into  the  boiler  (when  it  is  possible  to  do  so)  and  he  should 
look  for  pitting  and  grooving  of  plates,  test  all  braces,  and 
examine  all  inlets  and  outlets. 


HANDBOOK   ON    ENGINEERING.  449 


CHAPTER     XVII. 
USE  AND  ABUSE  OF  THE  STEAM=BOILER. 

Steam-boilers*  —  A  steam-boiler  may  be  defined  as  a  close 
vessel,  in  which  steam  is  generated.  It  may  assume  an  endless 
variety  of  forms,  and  can  be  constructed  of  various  materials. 
Since  the  introduction  of  steam  as  a  motive  power  a  great  variety 
of  boilers  has  been  designed,  tried  and  abandoned ;  while  many 
others,  having  little  or  no  merit  as  steam  generators,  they  have 
their  advocates  and  are  still  continued  in  use.-  Under  such  cir- 
cumstances, it  is  not  surprising  that  quite  a  variety  of  opinions 
are  held  on  the  subject.  This  difference  of  opinion  relates  not 
only  to  the  form  of  boiler  best  adapted  to  supply  the  greatest 
quantity  of  steam  with  the  least  expenditure  of  fuel,  but  also  to 
the  dimensions  or  capacity  suitable  for  an  engine  of  a  given  num- 
ber of  horse-power ;  and  while  great  improvements  have  been 
made  in  the  manufacture  of  boiler  materials  within  the  past 
fifteen  years,  yet  the  number  of  inferior  steam-boilers  seem  to 
increase  rather  than  diminish.  It  would  be  difficult  to  assign  any 
reasonable  cause  for  this,  except  that,  of  late  years,  nearly  the 
whole  attention  of  theoretical  and  mechanical  engineers  has  been 
directed  to  the  improvement  and  perfection  of  the  steam-engine, 
and  practical  engineers,  following  the  example  set  by  the  leaders, 
devote  their  energies  to  the  same  object.  This  is  to  be  regretted, 
as  the  construction  and  application  of  the  steam-boiler,  like  the 
steam-engine,  is  deserving  of  the  most  thorough  and  scien- 
tific study,  as  on  the  basis  of  its  employment  rest  some 
of  the  most  important  interests  of  civilization.  Until  quite 
recently,  the  idea  was  very  generally  entertained  that  the 
durely  mechanical  skill  required  to  enable  a  person  to  join 

29 


450  HANDBOOK    ON    ENGINEERING. 

together  pieces  of  metal,  and  thereby  form  a  steam-tight  and 
water-tight  vessel  of  given  dimensions,  to  be  used  for  the  gen- 
eration of  steam  to  work  an  engine,  was  all  that  was  needed ; 
experience  has  shown,  however,  that  this  is  but  a  small  portion  ol 
the  knowledge  that  should  be  possessed  by  persons  who  tarn  theii 
attention  to  the  design  and  construction  of  steam-boilers,  as  the 
knowledge  wanted  for  this  end  is  of  a  scientific  as  well  as  of  a 
mechanical  nature.  As  the  boiler  is  the  source  of  power  and  the 
place  where  the  power  to  be  applied  is  first  generated,  and  alsc 
the  source  from  which  the  most  dangerous  consequences  may  arise 
from  neglect  or  ignorance,  it  should  attract  the  special  attention 
of  the  designing  and  mechanical  engineer,  as  it  is  well  known 
that  from  the  hour  it  is  set  to  work,  it  is  acted  upon  by  destroy- 
ing forces,  more  or  less  uncontrollable  in  their  work  of  destruc- 
tion. These  forces  may  be  distinguished  as  chemical  and 
mechanical.  In  most  cases  they  operate  independently,  though 
they  are  frequently  found  acting  conjointly  in  bringing  about  the 
destruction  of  the  boiler,  which  will  be  more  or  less  rapid  accord- 
ing to  circumstances  of  design,  construction,  quality  of  material, 
management,  etc.  The  causes  which  most  affect  the  integrity  of 
boilers  and  limit  their  usefulness  are  either  inherent  in  the  mate- 
rial, or  due  to  a  want  of  skill  in  their  construction  and  manage- 
ment ;  they  may  be  enumerated  as  follows :  — 

First,  inferior  material ;  second,  slag,  sand  or  cinders  being 
rolled  into  the  iron ;  third,  want  of  lamination  in  the  sheets ; 
fourth,  the  overstretching  of  the  fiber  of  the  plate  on  one  side  and 
puckering  on  the  other  in  the  process  of  rolling,  to  form  the  circle 
for  the  shell  of  a  boiler ;  fifth,  injuries  done  the  plate  in  the  pro- 
cess of  punching ;  sixth,  damage  induced  by  the  use  of  the  drift- 
pin  ;  seventh,  carelessness  in  rolling  the  sheets  to  form  the  shell, 
as  a  result  of  which  the  seams,  instead  of  fitting  each  other 
exactly,  have  in  many  instances  to  be  drawn  together  by  bolts, 
which  aggravates  the  evils  of  expansion  and  contraction  when  the 


HANDBOOK    ON    ENGINEERING.  451 

boiler  is  in  use  :  eighth,  injury  done  the  plates  by  a  want  of  skill 
in  the  use  of  the  hummer  in  the  process  of  hand-riveting;  ninth, 
damage  done  in  the  process  of  calking. 

Other  causes  of  deterioration  are  unequal  expansion  and  con- 
traction, resulting  from  a  want  of  skill  in  setting  ;  grooving  in  the 
vicinity  of  the  seams ;  internal  and  external  corrosion  ;  blowing 
out  the  boiler  when  under  a  high-  pressure  and  filling  it  again  with 
cold  water  when  hot ;  allowing  the  lire  to  burn  too  rapidly  after 
starting,  when  the  boiler  is  cold ;  ignorance  of  the  use  of  the  pick 
in  the  process  of  scaling  and  cleaning ;  incapacity  of  the  safety- 
valve  ;  excessive  firing ;  urging  or  taxing  the  boiler  beyond  its 
safe  and  easy  working  capacity ;  allowing  the  water  to  become 
low,  and  thus  causing  undue  expansion  ;  deposits  of  scale  accum- 
ulating on  the  "parts  exposed  to  the  direct  action  of  the  fire, 
thereby  burning  or  crystallizing  the  sheets  or  shell ;  wasting  of  the 
material  by  leakage  and  corrosion ;  bad  design  and  construction 
of  the  different  parts  ;  inferior  workmanship  and  ignorance  in  the 
care  and  management.  All  these  tend  with  unerring  certainty  to 
limit  the  age  and  safety  of  steam  boilers.  On  account  of  want  of 
skill  on  the  part  of  the  designer  and  avarice  on  the  part  of  the 
manufacturer,  or  perhaps  both  reasons,  boilers  are  sometimes  so 
constructed  as  to  bring  a  riveted  seam  directly  over  the  fire,  the 
result  of  which  is  that  in  consequence  of  one  lap  covering  the 
other,  the  water  is  prevented  from  getting  to  the  one  nearest  the 
fire,  for  which  reason  the  lap  nearest  the  fire  becomes  hotter  and 
expands  to  a  much  greater  extent  than  any  other  part  of  the 
plate ;  and  its  constant  unequal  expansion  and  contraction,  as 
the  boiler  becomes  alternately  hot  and  cold,  inevitably  results  in  a 
crack.  Such  blunders  are  aggravated  by  the  scale  and  sediment 
being  retained  on  the  inside,  between  the  heads  of  the  rivets, 
which  should  be  properly  removed  in  cleaning. 

The  tendency  of  manufacturers  to  work  boilers  beyond  their 
capacity,  especially  when  business  is  driving,  is  too  great  in  this 


452  HANDBOOK    ON    ENGINEERING. 

country  ;  and  no  doubt  many  boiler  explosions  may  be  attributed 
to  this  cause.  Boilers  are  bought,  adapted  to  the  wants  of  the 
manufactory  at  the  time,  but,  as  business  increases,  machinery 
is  added  to  supply  the  demand  for  goods,  until  the  engine  is 
overtasked,  the  boiler  strained  and  rendered  positively  danger- 
ous. Then  again,  it  not  unfrequently  occurs  that  engines  in 
manufactories  are  taken  out  and  replaced  by  those  of  increased 
power,  while  the  boilers  used  with  the  old  engine  are  retained  in 
place,  with  more  or  less  cleaning  and  patching,  as  the  case  may 
require.  Now,  it  is  evident  to  any  practical  mind  that  boilers 
constructed  for  a  twenty-horse  power  engine  are  ill  adapted  to 
an  engine  of  forty-horse  power,  more  especially  if  those  boilers 
have  been  used  for  a  number  of  years.  In  order  to  supply 
sufficient  steam  for  the  new  engine,  with  a  cylinder  of  increased 
capacity,  the  boiler  must  be  worked  beyond  its  safe  working 
pressure,  consequently  excessive  heating  and  pressure  greatly 
weaken  it  and  endanger  the  lives  of  those  employed  in  the  vicinity. 
The  danger  and  impracticability  of  using  boilers  with  too 
limited  steam-room  may  be  explained  thus :  Suppose  the  entire 
steam-room  in  a  boiler  to  be  six  cubic  feet,  and  the  contents  of 
the  cylinder  which  it  supplies  to  be  two  cubic  feet ;  then  at  each 
stroke  of  the  piston  one-third  of  all  the  steam  in  the  boilers  is 
discharged,  and  consequently,  one-third  of  the  pressure  on  the 
surface  of  the  water  before  that  stroke  is  relieved ;  hence,  it  will 
be  seen  that  excessive  fires  must  be  kept  up  in  order  to  generate 
steam  of  sufficiently  high  temperature  and  pressure  to  supply  the 
demand.  The  result  is  that  the  boilers  are  strained  and  burned. 
Such  economy  in  boiler  power  is  exceedingly  expensive  in  fuel, 
to  say  nothing  of  the  danger.  Excessive  firing  distorts  the  fire- 
sheets,  causing  leakage,  undue  and  unequal  expansion  and  con- 
traction, fractures,  and  the  consequent  evils  arising  from  external 
corrosion.  Excessive  pressure  arises  generally  from  a  desire  on 
the  part  of  the  steam-user  to  make  a  boiler  do  double  the  work  for 


HANDBOOK    ON    ENGINEERING.  453 

which  it  was  originally  intended.  A  boiler  that  is  constructed  to 
work  safely  at  from  fifty  to  sixty  pounds  was  never  intended  to 
run  at  eighty  and  ninety  pounds  ;  more  especially  if  it  had  been 
in  use  for  several  years.  Boilers  deteriorated  by  age  should  have 
their  pressure  decreased,  rather  than  increased. 

One  of  the  first  things  that  should  be  done  in  manufacturing 
establishments  would  be  to  provide  sufficient  boiler  power  and,  in 
order  to  do  this,  the  work  to  be  done  ought  to  be  accurately  cal- 
culated and  the  engine  and  boilers  adapted  to  the  results  of  this 
calculation.  Steam  users  themselves  are  frequently  to  blame  for 
the  annoyances  and  dangers  arising  from  unsafe  boilers  and  those 
of  insufficient  capacity.  From  motives  of  false  economy  the v  are 
too  easily  swayed  in  favor  of  the  cheaper  article,  simply  because 
it  is  cheap,  when  they  should  consider  they  are  purchasing  an 
article  which,  of  almost  all  others,  should  be  made  in  the  most 
thorough  manner  and  of  the  best  material.  In  view  of  the  fearful 
explosions  that  occur  from  time  to  time,  every  steam  user  should 
secure  for  his  use  the  best  and  safest.  The  object  of  a  few 
dollars  as  between  the  work  of  a  good,  responsible  maker  and 
that  of  an  irresponsible  one,  should  not  for  one  moment  be 
entertained. 

It  is  very  bad  policy  for  steam-users  to  advertise  for  estimates 
for  steam-boilers,  or  to  inform  all  the  boiler-makers  in  the  town 
or  city  that  a  boiler  or  boilers  to  supply  steam  for  an  engine  of  a 
certain  size  is  needed,  because  in  this  way  steam-users  frequently 
find  themselves  in  the  hands  of  needy  persons,  who,  in  their 
anxiety  to  get  an  order,  will  sometimes  ask  less  for  a  boiler  than 
they  can  actually  make  it  for ;  consequently,  they  have  to  cheat 
in  the  material,  in  the  workmanship,  in  the  heating-surface  and  in 
the  fittings.  As  a  result,  the  boiler  is  not  only  a  continual  source 
of  annoyance,  but,  in  many  instances,  an  actual  source  of  danger. 
The  most  prudent  course,  and  in  fact  the  only  one  that  may  be 
expected  to  give  satisfaction,  is  to  contract  with  some  responsible 


454  HANDBOOK    ON    ENGINEERING. 

manufacturer  that  has  an  established  reputation  for  honesty, 
capability  and  fair  dealing,  and  who  will  not  allow  himself  to  be 
brought  in  competition  with  irresponsible  parties  for  the  purpose 
of  selling  a  boiler.  There  are  thousands  of  boilers  designed,  con- 
structed and  set  up  in  such  a  manner  as  to  render  it  utterly 
impossible  to  examine,  clean  or  repair  them.  Generally,  in  such 
cases,  in  consequence  of  imperfect  circulation,  the  water  is 
expelled  from  the  surface  of  the  iron  at  the  points  where  the 
extreme  heat  from  the  furnace  impinges,  and,  as  a  result,  the 
plates  become  overheated  and  bulge  outward,  which  aggravates 
the  evil,  as  the  hollow  formed  by  the  bulge  becomes  a  receptacle 
for  scale  and  sediment.  By  continued  overheating,  the  parts 
become  crystallized  and  either  crack  or  blister;  this,  if  not 
attended  to  and  remedied,  will  eventually  end  in  the  destruction 
of  the  boiler.  Many  boilers,  to  all  appearance  well  made  and  of 
good  material,  give  considerable  trouble  by  leakage  and  fracture, 
owing  to  the  severe  strains  of  unequal  expansion  and  contraction 
induced  by  the  rigid  construction,  the  result  of  a  want  of  skill  in 
the  original  design. 

DESIGN  OF  STEAM=BOILERS. 

It  has  become  a  general  assertion  on  the  part  of  writers  on  the 
steam-boiler  that  the  most  important  object  to  be  attained  in  its 
design  and  arrangement  is  thorough  combustion  of  the  fuel. 
This  is  only  partially  true  as  there  are  other  conditions  equally 
important,  among  which  are  strength,  durability,  safety,  economy 
and  adaptability  to  the  particular  circumstances  under  which  it  is 
to  be  used.  However  complete  the  combustion  may  be,  unless 
its  products  can  be  easily  and  rapidly  transferred  to  the  water, 
and  unless  the  means  of  escape  of  the  steam  from  the  surfaces  on 
which  it  is  generated  is  easy  and  direct,  the  boiler  will  fail  to 
produce  satisfactory  results,  either  in  point  of  durability  or 
economy  of  fuel. 


HANDBOOK    ON     KN(!  IN  KER1NG.  455 

Strength  means  the  power  to  sustain  the  internal  pressure  to 
which  the  boiler  may  be  subjected  in  ordinary  use,  and  under 
careful  and  intelligent  management.  To  secure  durability,  the 
material  must  be  capable  of  resisting  the  chemical  action  of  the 
minerals  contained  in  the  water,  and  the  boiler  ought  to  be 
designed  so  as  to  procure  the  least  strain  under  the  highest  state 
of  expansion  to  which  it  may  be  subjected  —  be  so  constructed 
that  all  the  parts  will  be  subjected  to  an  equal  expansion,  con- 
traction, push,  pull  and  strain,  and  be  intelligently  and  thoroughly 
cared  for  after  being  put  in  use.  These  objects,  however,  can 
only  be  obtained  by  the  aid  of  a  knowledge  of  the  principles  of 
mechanics,  the  strength  and  resistance  of  materials,  the  laws  of 
expansion  and  contraction,  the  action  of  heat  on  bodies,  etc. 
The  economy  of  a  steam  boiler  is  influenced  by  the  following  con- 
ditions: cost  and  quantity  of  the  material,  design,  character  of  the 
workmanship  employed  in  its  construction,  space  occupied,  capa- 
bility of  the  material  to  resist  the  chemical  action  of  the  ingredi- 
ents contained  in  the  water,  the  facilities  it  affords  for  the 
transmission  of  the  heat  from  the  furnace  to  the  water,  etc.  The 
safety  of  any  structure  depends  on  the  designer's  knowledge  of 
the  principles  of  mechanics,  the  resistance  of  materials  and  the 
action  of  bodies  as  influenced  by  the  elements  to  which  they  are 
exposed ;  and  in  the  case  of  steam  boilers,  the  safety  depends  on 
the  judgment  of  the  designer,  the  quality  of  the  material,  the 
character  of  the  workmanship  and  the  skill  employed  in  the  man- 
agement. Safety  is  said  to  be  incompatible  with  economy,  but 
this  is  undoubtedly  a  mistake,  as  an  intelligent  economy  includes 
permanence  and  seeks  durability.  Adaptability  to  the  peculiar 
purposes  for  which  they  are  to  be  used  is  one  of  the  first  objects 
to  be  sought  for  in  the  design  and  construction  of  any  class  of 
machines,  vessels  or  instruments,  and  it  is  undoubtedly  this  that 
gave  rise  to  the  great  variety  of  designs,  forms  and  modifications 
of  steam  boilers  in  use  at  the  present  day,  which  are,  with  very 


456  HANDBOOK    ON 

few   exceptions,  the  result  of  thought,    .study,  investigation  and 
experiment. 

FORMS  OF  STEAfl  BOILERS. 

According  to  the  well-known  law  of  hydrostatics,  the  pressure 
of  steam  in  a  close  cylindrical  vessel  is  exerted  equally  in  all 
directions.  In  acting  against  the  circumference  of  a  cylinder, 
the  pressure  must,  therefore,  be  regarded  as  radiating  from  the 
axis,  and  exerting  a  uniform  tensional  strain  throughout  the 
inclosing  material. 

Familiarity  with  steam  machinery,  more  especially  with  boil- 
ers,  is  apt  to  beget  a  confidence  in  the  ignorant  which  is  not 
founded  on  a  knowledge  of  the  dangers  by  which  they  uro  contin- 
ually surrounded  ;  while  contact  with  steam,  and  a  thoroughly 
elementary  knowledge  of  its  constituents,  theory  and  action,  only 
incline  the  intelligent  engineer  and  fireman  to  be  more  cautious 
and  energetic  in  the  discharge  of  their  duties.  Many  regard 
steam  as  an  incomprehensible  mystery ;  and  although  they  may 
employ  it  as  a  power  to  accomplish  work,  know  little  of  its 
character  or  capabilities.  Steam  may  be  managed  by  common 
sense  rules  as  well  as  any  other  power ;  but  if  the  laws  which 
regulate  its  use  are  violated,  it  reports  itself,  and  often  in  louder 
tones  than  is  pleasant.  If  steam-boilers  in  general  were  better 
cared  for  than  they  are,  their  working  age  might  be  greatly  in- 
creased. Deposits  of  incrustation,  small  leaks  and  slight  cor- 
rosion, are  too  often  neglected  as  matters  of  little  consequence, 
but  they  are  the  forerunners  of  expensive  repairs,  delay  and 
disaster. 

SETTING  STEAM-BOILERS. 

While  engineers  differ  very  much  in  opinion  respecting  the  best 
manner  of  setting  boilers,  they  all  readily  allow  that  the  results 
obtained,  as  regards  economy  of  fuel  and  the  generation  of  steam, 


HANDBOOK    ON    ENGINEERING.  457 

depend  in  a  great  measure  on  the  arrangement  of  the  setting. 
Particularly  is  this  the  case  with  horizontal  tubular  boilers,  and 
there  have  been  numerous  plans  introduced  to  obtain  a  maximum 
of  steam  with  a  minimum  of  fuel.  Some  of  the  most  practical 
designs  and  best  laid  plans  are  frequently  rendered  useless  for 
want  of  knowledge  on  the  part  of  those  whose  duty  it  is  to  exe- 
cute or  carry  them  out.  This  has  perhaps  been  more  frequently 
the  case  as  regards  the  setting  of  steam  boilers  than  any  other 
class  of  machines,  as  it  is  customary  for  owners  of  steam  boilers 
to  depend  too  much  on  the  knowledge  of  masons  and  bricklayers ; 
consequent!}',  a  great  many  blunders  have  been  made  which 
necessitated  changes  in  the  size  of  gratebars,  alteration  of  brick- 
work, alteration  of  flues,  chimney,  etc.,  with  a  list  of  other  annoy- 
ances, such  as  insufficiency  of  steam,  poor  draught,  or  something 
else.  In  setting  or  putting  in  boilers,  all  the  surface  possible  should 
be  exposed  to  the  action  of  the  heat  of  the  fire,  not  only  that  the 
heat  may  be  thus  completely  absorbed,  but  that  a  more  equal  ex- 
pansion and  contraction  of  the  structure  may  be  obtained.  Long 
boilers  are  often  hung  by  means  of  loops  riveted  to  the  top  of 
them  and  connected  to  crossbeams  and  arches  resting  on  masonry 
above  them,  by  means  of  hangers.  This  is  a  very  mischievous 
arrangement,  unless  turn-buckles,  or  some  other  contrivance,  are 
used  to  maintain  a  regular  strain  on  all  the  hangers,  as  long  boil- 
ers exposed  to  excessive  heat  are  apt  to  lengthen  on  the  lower 
side  and  relieve  the  end  hangers  of  any  weight;  consequently, 
the  whole  strain  is  transmitted  to  the  central  hanger,  which  has  a 
tendency  to  draw  the  boiler  out  of  shape  —  in  many  instances 
inducing  excessive  leakage,  rupture,  and,  eventually,  explosion. 

DEFECTS   IN   THE  CONSTRUCTION  OF   STEAM   BOILERS. 

The  following  cuts  illustrate  some  of  the  mechanical  defects 
that  impair  the  strength  and  limit  the  safety  and  durability  of 


458 


HANDBOOK    ON    ENGINEERING. 


steam  boilers.  All  punched  holes  are  conical,  and  unless  the 
sheets  are  reversed  after  being  punched,  so  as  to  bring  the 
small  sides  of  the  holes  together,  it  will  be  impossible  to  till  them 
with  the  rivets.  Fig.  1  shows  the  position  of  the  rivet  in  the 
hole  without  the  sheets  being  reversed  ;  and  it  will  be  observed 
that,  as  very  little  of  the  rivet  bears  against  the  material,  the  ex- 
pansion and  contraction  of  the  boiler  have  a  tendency  to  work  it 
loose.  It  is  apparent  that  such  a  seam  would  not  possess  over 
one-third  the  strength  that  it  would  if  the  holes  in  the  sheets 


Fig.  1. 


Fisr.  o. 


Fig.  5, 


Fig.  6. 


were  reversed  and  thoroughly  filled  with  the  rivet,  as  shown  in 
Fig.  2.  Fig.  o  represents  what  is  known  in  boiler-making  as  a 
blind-hole,  which  means  that  the  holes  do  not  come  opposite 
each  other  when  the  seams  are  placed  together  for  the  purpose  of 
riveting.  Fig.  4  shows  the  position  of  the  rivet  in  the  blind-hole 
after  being  driven.  It  will  be  observed  that  the  heads  of  the 
rivet,  in  consequence  of  its  oblique  position  in  the  hole,  bear  only 
on  one  side,  and  that  even  the  bearing  is  very  limited,  and 
through  the  expansion  and  contraction  of  the  boiler,  is  liable  to 


HANDBOOK    ON    ENGINEERING.  459 

work  loose  and  become  leaky.  Such  :i  seam  would  be  actually 
weaker  than  that  represented  in  Fig.  1.  Fig.  5  shows  the  metal 
distressed  and  puckered  on  each  side  of  the  blind-hole  in  the 
sheets,  which  is  the  result  of  efforts  on  the  part  of  the  boiler- 
maker,  by  the  use  of  the  drift-pin,  to  make  the  holes  correspond 
for  the  purpose  of  inserting  the.  rivet.  Fig.  6  shows  the  metal 
broken  through  by  the  same  means.  Now,  it  will  be  observed 
that  nearly  all  the  above  defects  are  the  result  of  ignorance  and 
carelessness,  showing  a  want  of  skill  in  laying  out  the  work,  as 
well  as  a  want  of  proper  appliances  for  that  purpose.  The  evils 
arising  from  such  defects  are  greatly  aggravated  by  the  fact  that 
they  are  all  concealed,  frequently  defying  the  closest  scrutiny,  and 
are  only  revealed  by  those  forces  which  unceasingly  act  on  boilers 
when  in  use.  Such  pernicious  mechanical  blunders  ought  to  be 
condemned,  as  they  are  always  the  forerunners  of  destruction 
und  death.  There  can  be  no  reason  why  boilers  should  not  be 
constructed  with  the  same  degree  of  accuracy,  judgment  and  skill 
as  is  considered  so  essential  for  all  other  classes  of  machinery. 

IMPROVEMENTS  IN  STEAM=BOILERS. 

Until  quite  recently  the  steam  boiler  has  undergone  very  little 
improvement.  This  arose,  perhaps,  from  the  fact  that  men  of 
intelligence  and  mechanical  genius  directed  their  thoughts  and 
labors  to  something  more  inviting  and  less  laborious  than  the 
construction  of  steam  boilers.  Consequently,  that  branch  of 
mechanics  was  left  almost  entirely  to  a  class  of  men  that  had  not 
the  genius  to  rise  in  their  profession  or  improve  much  in  anything 
they  attempted.  As  a  result  ignorance,  stupidity  and  a  kind  of 
brute  force  were  the  predominant  requirements  in  the  construc- 
tion of  the  steam  boiler  ;  but  within  the  past  few  years  this  state 
of  things  has  been  changed,  as  some  very  important  improvements 
have  been  made,  not  only  in  the  manufacture  of  the  material  of 
which  boilers  are  made,  but  also  in  the  mode  of  constructing 


460  HANDBOOK    ON    ENGINEERING. 

them.  The  imposing,  powerful  and  accurate  boiler  machinery  in 
use  at  the  present  time  is  an  evidence  that  the  attention  of  emi- 
nent mechanics  and  manufacturers  is  directed  to  the  steam  boiler, 
and  that  in  the  future  its  improvement  will  keep  pace  with  that  of 
the  steam  engine. 

Boiler-plate  is  now  rolled  of  sufficient  dimensions  to  form  the 
rings  for  boilers  of  any  diameter  with  only  one  seam,  obviating 
the  necessity  of  bringing  riveted  seams  in  contact  witk  the  fire, 
as  was  usually  the  case  in  former  times.  In  the  manner  of  laying 
off  the  holes  for  the  rivets,  accurate  steel  gauges  have  taken  the 
place  of  the  old-fashioned  wooden  templet,  thereby  removing  the 
evils  induced  by  blind-holes,  and  obviating  the  necessity  of  using 
the  drift-pin.  So,  also,  in  the  method  of  bending  the  sheets  to 
form  the  requisite  circle  —  with  a  better  class  of  machinery,  the 
work  is  now  mo  re  accurately  performed.  The  old  process  of  chip- 
ping is,  in  nearly  all  the  large  boiler-shops,  superseded  by  planing 
the  bevels  on  the  edge  of  "the  sheet,  preparatory  to  calking.  Recent 
improvements  in  "  calking  "  have  resulted  in  perfect  immunity  from 
the  injuries  formerly  inflicted  on  boilers  in  that  process. 
In  most  establishments  of  any  repute  in  this  country,  riveting  is 
done  by  machinery,  which  is  (as  is  well  known  to  all  intelligent 
mechanics)  very  much  superior  to  hand-riveting.  It  is  only 
small  shops  that  enter  into  rivalry  to  secure  orders  and  build 
cheap  boilers,  using  poor  material  and  an  inferior  quality  of 
mechanical  skill,  that  use  the  same  old  crude  appliances  —  in 
many  cases  the  merest  makeshifts  —  that  were  in  use  a  quarter  of 
a  century  ago,  and  constructed  without  regard  to  any  of  the  rules 
of  design  that  are  considered  so  essential  in  appliances  for  the 
construction  of  all  other  classes  of  machinery.  Every  engineer 
should  inform  himself  on  the  subject  of  the  safe  working  pressure 
of  boilers,  and  when  he  finds  the  limit  of  safety  has  been  reached, 
he  should  promptly  inform  his  employer  and  use  his  influence  to 
have  the  boiler  worked  within  the  bounds  of  safety. 


HANDBOOK    ON    ENGINEERING. 


461 


To  find  the  heating  surface  of  a  water  tube  boiler :  — 

Rule. —  Add  the  combined  outside  area  of  the  tubes  in  square 
feet  to  one-half  the  area  of  the  shell  of  the  steam  drum  in  square 
feet  and  the  sum  will  give  the  total  heating  surface.. 

Example  J*  —  What  is  the  heating  surface  of  a  water  tube 
boiler  having  fifty  tubes,  each  three  inches  outside  diameter  and 
fifteen  feet  long,  and  the  steam  drum  thirty-two  inches  in 
diameter  and  fifteen  feet  long  ? 

Operation.  —  3  X  3.1416  equals  9.4248  inches,  the  circumfer- 
ence of  one  tube.  15  X  12  equals  180  inches  the  length  of  one 

9. 4248  X  180 
tube.   -     — TTT —   -  equals  11.781    square  feet  in  one  tube,  and 

11.781  X  50  equals  589.05  square  feet  of  heating  surface  in  fifty 

32  X  3. 1410 

tubes.     Then,  -     —^ —    -  equals  8.3770  linear  feet  the  circum- 
ference of  the  steam  drum  and  8.3770.  X  15  equals  125.004  square 

125.064 
feet  of  heating  surface  in  steam  drum,  and ~ equals  62.832 

square  feet,  half  the  heating  surf  ace  of  steam  drum. 

Then,  589.05  plus  02.832  equals  651.882  square  feet,  the  total 
heating  surface.  Answer. 


STRENGTH  OF  RIVETED  SEAflS. 

The  strength  of  a  riveted  seam  depends  very  much  upon  the 
arrangement  and  proportion  of  the  rivets ;  but  with  the  best 
design  and  construction,  the  seams  are  always  weaker  than  the 
solid  plate,  as  it  is  always  necessary  to  cut  away  a  part  of 
the  plate  for  the  rivet  holes,  which  weakens  the  holes  in  three 
ways :  1st,  by  lessening  the  amount  of  material  to  resist  the 
strains;  2d,  by  weakening  that  left  between  the  holes;  3d,  by 
disturbing  the  uniformity  of  the  distribution  of  the  strains. 


462  HANDBOOK    ON    FA<!  I  \  KERIXG. 

COMPARATIVE  STRENGTH  OF  SINGLE  AND  DOUBLE 
RIVETED  SEAMS. 

On  comparing  the  strength  of  plates  with  riveted  joints,  it  will 
be  necessary  to  examine  the  sectional  areas  taken  in  a  line  through 
the  rivet-holes,  with  the  section  of  the  plates  themselves.  It  is 
obvious  that  in  perforating  a  line  of  holes  along  the  edge  of  a 
plate,  we  must  reduce  its  strength.  It  is  also  clear  that  the  plate 
so  perforated  will  be  to  the  plate  itself  nearly  as  the  areas  of  their 
respective  sections,  with  a  small  deduction  for  the  irregularities 
of  the  pressure  of  the  rivets  upon  the  plate ;  or,  in  other  words, 
the  joint  will  be  reduced  in  strength  somewhat  more  than  in  the 
ratio  of  its  section  through  that  line  to  the  solid  section  of  the 
plate.  It  is  also  evident  that  the  rivets  cannot  add  to  the  strength 
of  the  plates,  their  object  being  to  keep  the  two  surfaces  of  the 
lap  in  contact.  When  this  great  deterioration  of  strength  at  the 
joint  is  taken  into  account,  it  cannot  but  be  of  the  greatest 
importance  that  in  structures  subject  to  such  violent  strains  as 
boilers,  the  strongest  method  of  riveting  should  be  adopted.  To 
ascertain  this,  a  long  series  of  experiments  was  undertaken  by 
Mr.  Fairbairn.  There  are  two  kinds  of  lap-joints,  single  and 
double-riveted.  In  the  early  days  of  steam-boiler  construction, 
the  former  were  almost  universally  employed ;  but  the  greater 
strength  of  the  latter  has  since  led  to  their  general  adoption  for 
all  boilers  intended  to  sustain  a  high  steam  pressure.  A  riveted 
joint  generally  gives  way  either  by  shearing  off  the  rivets  in  the 
middle  of  their  length,  or  by  tearing  through  one  of  the  plates  in 
the  line  of  the  rivets. 

In  a  perfect  joint,  the  rivets  should  be  on  the  point  of  shearing 
just  as  the  plates  were  about  to  tear ;  but,  in  practice,  the  rivets 
are  usually  made  slightly  too  strong.  Hence,  it  is  an  established 
rule  to  employ  a  certain  number  of  rivets  per  linear  foot,  which 
for  ordinary  diameters  and  average  thickness  of  plate,  are  about 


HANDBOOK    ON    ENGINEERING.  463 

six  per  foot  or  two  inches  from  center  to  center ;  for  larger 
diameters  and  heavier  iron,  the  distance  between  the  centers 
is  generally  increased  to,  say  2  j-  or  2J-  inches ;  but  in  such 
cases  it  is  also  necessary  to  increase  the  diameter  of  the  rivet, 
for  while  J,  or  even  J  inch  rivets  will  answer  for  small  diameters 
and  light  plate,  with  large  diameters  and  heavy  plate,  experi- 
ence has  shown  it  to  be  necessary  to  use  J  to  J  rivets.  If 
these  are  placed  in  a  single  row,  the  rivet  hqles  so  nearly 
approach  each  other  that  the  strength  of  the  plates  is  much 
reduced ;  but  if  they  are  arranged  in  two  lines,  a  greater  number 
may  be  used,  more  space  left  between  the  holes  and  greater 
strength  aud  stiffness  imparted  to  the  plates  at  the  joint. 
Taking  the  value  of  the  plate  before  being  punched,  at  100,  by 
punching  the  plate  it  loses  44  per  cent  of  its  strength  ;  and,  as  a 
result,  single-riveted  seams  are  equal  to  56  per  cent,  and  double- 
riveted  seams  to  70  per  cent  of  the  original  strength  of  the  plate. 
It  has  been  shown  by  very  extensive  experiments  at  the  Brooklyn 
Navy  Yard,  and  also  at  the  Stevens  Institute  of  Technology, 
Hoboken,  N.  J.,  that  double-riveted  seams  are  from  16  to  20  per 
cent  stronger  than  single-riveted  seams  —  the  material  and  work- 
manship being  the  same  in  both  cases : 

Taking  the  strength  of  the  plate  at 100 

The  strength  of  the  double-riveted  joint  would  then  be  .      .        70 
The  strength  of  the  single-riveted  would  be       .....       56 

To  find  the  thickness  of  plates  for  the  shell  of  a  cylindrical 
boiler  for  a  required  safe  working  pressure  in  pounds  per  square 
inch :  — 

Rule*  —  Multiply  the  required  pressure  per  square  inch  by  the 
radius  of  the  shell  in  inches,  and  by  the  constant  number  6  for 
single  riveted  side  seams,  and  divide  the  last  product  by  the 
tensile  strength  of  the  plates.  For  double  riveted  side  seams  use 
the  constant  number  5  instead  of  6. 

Example  1*  —  What  should  be  the  thickness  of  plates  for  a  boiler 
60  inches  in  diameter,  with  single  riveted  side  seams,  for  a  work- 


HANDBOOK    ON    ENGINEERING. 

ing  pressure  of  125  pounds  per  square  inch,  the  tensile  strength 
of  the  plates  being  60,000  pounds  per  square  inch? 

125  X  30  X  6 
Operation,  —  --  60~000  --  e(luals  -370  or  3/8  *n-     Answer. 

Example  2,  —  What  should  be  the  thickness  of  plates  for  a 
boiler  60  inches  diameter,  with  double  riveted'side  seams,  for  a 
working  pressure  of  150  pounds  per  square  inch,  the  tensile 
strength  of  plates  being  60,000  pounds  per  square  inch. 

150  X  30  X  5 
Operation,  -          6Q  QOQ  --  equals  .375  or  3/8  in.     Answer. 

The  following  formulas,  equivalent  to  those  of  the  British 
Board  of  Trade,  are  given  for  the  determination  of  the  pitch, 
distance  between  rows  of  rivets,  diagonal  pitch,  maximum  pitch, 
and  distance  from  centers  of  rivets  to  edge  of  lap  of  single  and 
double  riveted  lap  joints,  for  both  iron  and  steel  boilers:  — 

Let  p  =  greatest  pitch  of  rivets,  in  inches  ; 

n  =  number  of  rivets,  in  one  pitch  ; 
|)d  —  diagonal  pitch,  in  inches  ; 
d  =  diameter  of  rivets,  in  inches  ; 
T  —  thickness  of  plate,  in  inches; 
V=  distance  between  rows  of  rivets,  in  inches  ; 
E  =  distance  from  edge  of  plate  to  center  of  rivet,  in  inches. 

TO    DETERMINE    ^HE    PITCH. 

Iron  plates  and  iron  rivets  — 

«:Z2X.  7854  X?*   , 

rpp=s,rr      —  y—     -  +  d. 

Example  :  First,  for  single-riveted  joint  — 

Given,    thickness  of    plate    (!T)=£  inch,   diameter   of   rivet 

—  J  inch.     In  this  case,  n  =  l.     Required,  the  pitch. 
Substituting  in  formula,  and  performing  operation  indicated. 


Piteh  =  +    =  2.077  inches. 

2" 


HANDBOOK    ON    ENGINEERING.  4(l5 

For  double-riveted  joint  — 

Given,  £=-J  inch,  and  d  =  %%  inch.  In  this  case,  n  =  2. 
Then  — 

Pitch  =  («)'X.7864X2  +  H  =  2_886  inches> 

?       , 

For  steel  plates  and  steel  rivets  :  — 

23  X  (V  X  n    . 
P  =       28  XT-    +  d' 

Example,  for  single-riveted  joint  :  Given,  thickness  of  plate  —  \ 
inch,  diameter  of  rivet  =  if  inch.  In  this  case,  ?i=l. 
Then  — 


Example,  for  double-riveted  joint  :  Given,  thickness  of  plate  —  i 
inch,  diameter  of  rivet  =  J  inch,     n  =  2.     Then  — 

2         =  ^5  inches. 


FOR    DISTANCE    FROM    CENTER    OF    RIVET    TO    EDGE    OF    LAP. 

3X<* 
~2~ 

Example  :  Given,  diameter  of  rivet  (d)  =  |  inch  ;  required,  the 
distance  from  center  of  rivet  to  edge  of  plate. 

E=3X^=  1.312  inches, 
^ 

for  single  or  double  riveted  lap  joint. 

FOR    DISTANCE    BETWEEN    ROWS    OF    RIVETS. 

The  distance  between  lines  of  centers  of  rows  of  rivets  for 
double,  chain-riveted  joints  (F)  should  not  be  less  than  twice  the 
diameter  of  rivet,  but  it  is  more  desirable  that  V  should  not  be 

less  than—       —  • 
t 

SO 


466  .    HANDBOOK    ON    ENGINEERING. 

Example  under  latter  formula:   Given,   diameter  of  rivet  = 
inch,  then  — 


For  ordinary,  double,  zigzag  -riveted  joints, 


10 

Example :   Given,  pitch  =  2 .85  inches,  and  diameter  of  rivet  =  | 
inch,  then  — 


r=  IXJH^       il>=1.4«7inche, 


DIAGONAL    PITCH. 

For  double,  zigzag-riveted  lap  joint.     Iron  and  steel. 

(ij>  -f  4d 

~Jo~ 

pjxample:   Given,  pitch  =  2.  85  inches,  and  d  =  %  inch,  then 


MAXIMUM    PITCHES    FOR    RIVETED    LAP    JOINTS. 

For  single-riveted  lap  joints,  maximum  pitch  =(1.31  X  T)  +  lf  . 

For  double-riveted  lap  joints,  maximum  pitch  =(2.62  X  T)  -f  1|  . 

Example:  Given  a  thickness  of  plate  =  J  inch,  required,  the 
maximum  pitch  allowable. 

For  single-riveted  lap  joint,  maximum  pitch  =  (1.81  X  4-)  + 
If  =  2.28  inches. 

For  double-riveted  lap  joint,  maximum  pitch  =  (2.62  X  |)  + 
14  =  2.935  inches. 

o 

The  following  tables,  taken  from  the  handbook  of  Thomas  W. 
Traill,  entitled  "Boilers,  Marine  and  Land,  their  Construction 


HANDBOOK   ON    ENGINEERING. 


467 


and  Strength,"  may  be  taken  for  use  in  single  and  double  riveted 
joints,  as  approximating  the  formulas  of  the  British  Board  of 
Trade  for  such  joints :  — 


IRON  PLATES  AND   IRON  RIVETS. 

DOUBLK-RIVKTKI)    LAP    JOINTS. 


Distance  between  rows 

Center  of 

of  rivets. 

Thickness 

Diameter 

Pitch  of 

rivets  to 

of  plates. 

of  rivets. 

rivets. 

edge  of 

plates. 

Zigzag 

Chain 

riveting. 

riveting. 

r 

d 

P 

E 

V 

V 

1  6" 

1 

2.272 

.937 

1.145 

1.750 

u 

3  2 

2.386 

.984                1.202 

1.812 

l" 

ft 

2.500 

1.031               1.260 

1.875 

tt 

P 

2.613 

1.078 

.317 

1.937 

"iL(i" 

2.727 

1.125 

.374 

2.000 

l| 

n 

2.826 

1.171 

.426 

2.062 

i" 

13. 

2.886 

1.218 

.465 

2.125 

if 

2.948 

1.265 

.504              2.187 

"A 

%                  3.013 

1.312 

.544             2.250 

11 

If               3.079 

1.359 

.585 

2.312 

1 

It         ;       3.14-6 

1.406 

.626 

2.375 

H 

1.453 

.667 

2.437 

ti 

\*               3.284 

1.500 

.709             2.500 

il 

laV               3.355 

1.546 

.751 

2.562 

«  ^ 

liV               3.426 

1.593 

.794 

2.625 

M 

1-3*-               3.498 

1.640 

1.836 

2.687 

6 

U                  3.571 

1.687 

1.879 

2.750 

il 

l-352-               3.645 

1.734 

1.923 

2.812 

1 

1W               3.718 

1.781 

1.966 

2.875 

If 

1-3L               3.793 

1.828 

2.009 

2.937 

ft 

14                 3.867 

1.875 

2.053 

3.000 

II 

l-3a-               3.942 

1.921 

2.096 

3.062 

l-5d-               4.018 

1.968 

2.140 

3.125 

468 


HANDBOOK    ON    ENGINEERING. 


ZIGZAG  RIVETING. 


CHAIN  RIVETING. 


-f~M — 


o  -e-- 


HANDBOOK    ON    ENGINEERING. 
IRON  PLATES  AND  IRON   RIVETS. 

SINGLE-RIVETED  LAP  JOINTS, 


469 


7 

i 

^ 

\% 

p        .-    . 

LET 

C^ 

(i)   ^!Q^. 

i 

g 

w 

V>       \J/ 

'uT 

^ 

/a 

^ 

1 

Thickness  of             Diameter  of 

Pitch  of           Center  of  rivets  to 

plates.                       rivets. 

rivets.                edge  of  plates. 

T  - 

d 

P 

E 

j1 

ft 

.524 

.937 

A 

2_L 
3  2 

.600 

.984 

A 

.676 

.031 

0 

II 

.753 

.078 

§ 

| 

.829 

.125 

If 

.905 

.171 

.981 

.218 

|i 

2.036 

.265 

i 

1 

2.077 

.312 

II 

!! 

2.120 

.359 

i  if 

2.164 

.406 

if 

11 

2.210 

.453 

| 

i 

2.256 

.500 

f  2 

i-1- 

2.304 

.546 

16 

hV 

2.352 

.593 

3  2 

2.400 

.640 

lr 

2.450 

.687 

2.5. 

2.500 

.734 

IB 

l^Sj 

2.550 

.781 

il 

J_i. 

2.601 

.828 

i* 

ll2 

2.652 

.875 

if 

l-3a. 

2.703 

.921 

it 

h5e 

2.755 

.968 

470  JIANDHOOK    ON    ENGINEK1M  N(! . 

STEEL  PLATE  AND  STEEL  RjVETS. 

SINGLE-RIVETED   LAP   JOINTS. 


•-*••*• 

i* 

-•i- 


Thickness  of 
plates. 

Diameter  of 
.  rivets. 

Pitch  of 
rivets. 

Center  of  rivets 
to  edge  of 
plates. 

T 

rf 

P 

i 

H 

1.562 

.031 

£2 

.633 

.078 

JL.! 

;] 

.704 

.125 

11. 

ft 

.775 

.171 

§ 

.846 

.218 

if 

3  2 

.917 

.265 

la 

.988 

.312 

I! 

fl 

2.036 

.359 

L 

II 

2.071 

.406 

li 

2.108 

.453 

A 

1 

2.146 

.500 

II 

2.186 

.546 

1-jL 

2.227 

.593 

2JL 

1-^- 

2.269 

.640 

fl 

l| 

2.312 

.687 

|f 

H&2 

2.356 

.734 

2.400 

.781 

25 

2.445 

.828 

rl 

2.500 

.875 

£2- 

1A 

2.562 

.921 

|* 

1-5.. 

2.623 

.968 

25 

Ifl 

2.687 

2.015 

a 

If' 

2.750 

2.062 

HANDBOOK    ON    ENGINEERING. 


471 


STEEL  PLATE  AND   STEEL  RIVETS. 

DOUBLE -RIVETED    LAP   JOINTS. 


Distance  between  rows 

Center  of 

of  rivets. 

Thickness 

Diameter 

Pitch  of 

rivets  to 

of  plates. 

of  rivets. 

rivets. 

edge  of 
plates. 

Zigzag 

Chain 

riveting. 

riveting. 

T 

<Z 

P 

E 

V 

Y 

ft 

11 

2.291 
2.395 

.031 

.078 

.187 
.240 

1.875 
1.937 

1 

5 

2.500 

.125 

.295 

2.000 

ft 

H 

2.604 

.171 

.349 

2.062 

V<f 

16 

2.708 

.218 

.403 

2.125 

P 

P 

2.803 
2.850 

265 
.312 

.453 

.487 

2.187 
2.250 

12. 

3  2 

|| 

2.900 

.359 

.522 

2.312 

W 

10 

2.953 

.406 

.558 

2.375 

H 

II 

3.008 

.453 

.595 

2.437 

1 

1 

3.064 

.500 

.631 

2.500 

|i 

ift 

3.122 

.546 

.669 

2.562 

I  « 

i-,V 

3.181 

.593 

.707 

2.625 

la 

tt 

3.241 

.640 

.745 

2.687 

| 

H 

3.302 

.684 

.784 

2.750 

If 

i& 

3.364 

.734 

.823 

2.812 

1  6 

h:V 

3.427 

.781 

.863 

2.375 

B 

& 

3  490 

.828 

.902 

2.937 

I 

H 

3.554 

.875 

.942 

3.000 

2  n 
';<  2 

*& 

3.618 

.921 

.981 

3-062 

ti 

1ft 

3.683 

.968 

2.021 

3.125 

ft 

ill 

3.748 

2.015 

2.061 

3.187 

i 

if 

3.814 

2.062 

2.102 

3.250 

472 


HANDBOOK    ON    ENGINEERING. 


ZIGZAG  RIVETING". 


I 

1                                             '""" 

1 

1 

3 

I                                 1 

6   -&-" 

E 

-i— 

v 

i 

?. 

)     O     <. 

E 

I 

CHAIN   RIVETING. 


o  -e- 


.± — 


HANDBOOK  ON  KN<  JI NKK1MNG.  473 

STRENGTH  OF  STAYRD  AND  FLAT  BOILER  SURFACES. 

The  sheets  that  form  the  sides  of  fire-boxes  are  necessarily 
exposed  to  a  vast  pressure,  therefore,  some  expedient  has  to  be 
devised  to  prevent  the  metal  at  these  parts  from  bulging  out. 
Stay-bolts  are  generally  placed  at  a  distance  of  4|  inches  from 
center  to  center,  all  over  the  surface  of  fire-boxes,  and  thus  the 
expansion  or  bulging  of  one  side  is  prevented  by  the  stiffness  or 
rigidity  of  the  other.  Now,  in  an  arrangement  of  this  kind,  it 
becomes  necessary  to  pay  considerable  attention  to  the  tensile 
strength  of  the  stay-bolts  employed  for  the  above  purpose,  since 
the  ultimate  strength  of  this  part  of  the  boiler  is  now  transferred 
to  them,  it  being  impossible  that  the  boiler  plates  should  give  way 
unless  the  stay-bolts  break  in  the  first  instance.  Accordingly, 
the  experiments  that  have  been  made  by  way  of  test  of  the 
strength  of  stay-bolts,  possess  the  greatest  interest  for  the  practi- 
cal engineer.  Mr.  Fairburn's  experiments  are  particularly  val- 
uable. He  constructed  two  flat  boxes,  22  inches  square.  The 
top  and  bottom  plates  of  one  were  formed  of  -J  inch  copper,  and 
of  the  other,  f  inch  iron.  There  was  a  2J  inch  water-space  to  each, 
with  if  inch  iron-stays  screwed  into  the  plates  and  riveted  on  the 
ends.  In  the  first  box  the  stays  were  placed  five  inches  from 
center  to  center,  and  the  two  boxes  tested  by  hydraulic  pressure. 
In  the  copper  box,  the  sides  commenced  to  bulge  at  450  Ibs. 
pressure  to  the  sq.  in.  ;  and  at  815  Ibs.  pressure  to  the  sq.  in. 
the  box  burst,  by  drawing  the  head  of  one  of  the  stays  through 
the  copper  plate.  In  the  second  box,  the  stays  were  placed  at 
4-inch  centers;  the  bulging  commenced  at  515  Ibs.  pressure  to 
the  sq.  in.  The  pressure  was  continually  augmented  up  to  1,000 
Ibs.  The  bulging  between  the  rivets  at  that  pressure  was  one- 
third  of  an  inch ;  but  still  no  part  of  the  iron  gave  way.  At 
1,625  Ibs.  pressure  the  box  burst,  and  in  precisely  the  same  way 
as  in  the  first  experiment  —  one  of  the  stays  drawing  through  the 


474  HANDBOOK    ON    ENGINEERING . 

iron  plate  and  stripping  the  thread  in  plate.  These  experiments 
prove  a  number  of  facts  of  great  value  and  importance  to  the 
engineer.  In  the  first  place,  they  show  that  with  regard  to  iron 
stay-bolts,  their  tensile  strength  is  at  least  equal  to  the  grip  of 
the  plate. 

The  grip  of  the  copper  bolt  is  evidently  less.  ^  As  each  stay, 
in  the  first  case,  bore  the  pressure  on  an  area  of  5  x  5  =  25  square 
inches,  and  in  the  second  on  an  area  4x4  —  16  sq.  inches,  the 
total  strains  borne  by  each  stay  were,  for  the  first,  815x25  = 
20,375  pounds  on  each  stay;  and  for  the  second,  1,625  x  10  = 
26,000  Ibs.  on  each  stay.  These  strains  were  less,  however,  than 
the  tensile  strength  of  the  stays,  which  would  be  about  28,000 
Ibs.  The  properly  stayed  surfaces  are  the  strongest  part  of  boil- 
ers, when  kept  in  good  repair. 

BOILER-STAYS. 

Advantage  is  usually  taken  of  the  self-supporting  property  of 
the  cylinder  and  sphere,  which  enables  them,  in  most  cases,  to  be 
made  sufficiently  strong  without  the  aid  of  stays  or  other  support. 
But  the  absence  of  this  self-sustaining  property  in  flat  surfaces 
necessitates  their  being  strengthened  by  stays  or  other  means. 
Even  where  a  flat  or  slightly  dished  surface  possesses  sufficient 
strength  to  resist  the  actual  pressure  to  which  it  is  subjected,  it  is 
yet  necessary  to -apply  stays  to  provide  against  undue  deflection 
or  distortion,  which  is  liable  to  take  place  to  an  inconvenient  de- 
gree, or  to  result  in  grooving,  long  before  the  strength  of  plates 
or  their  attachments  is  seriously  taxed.  Boiler  stays,  in  any 
case,  are  but  substitutes  for  real  strength  of  construction.  They 
would  be  of  no  service  applied  to  a  sphere  subject  to  internal 
pressure  ;  and  the  power  of  resistance  would  be  exactly  that  of 
the  metal  to  sustain  the  strain  exerted  upon  all  its  parts  alike. 
The  manner  in  which  stays  are  frequentty  employed  renders  them 
a  source  of  weakness  rather  than  an  element  of  strength.  When 


HANDBOOK    ON    ENGINEERING. 


475 


the  strain  is  direct  the  power  of  resistance  of  the  stay  is  equal  to 
the  weight  it  would  sustain  without  tearing  it  asunder ;  but  when 
the  position  of  the  stay  is  oblique  to  the  point  of  resistance,  any 
calculation  of  their  theoretic  strength  or  value  is  attended  with 
certain  difficulties.  All  boilers  should  be  sufficiently  stayed  to 
insure  safety,  and  the  material  of  which  they  are  made,  their 
shape,  strength,  number,  location  and  mode  of  attachment  to  the 
boiler,  should  all  be  duly  and  intelligently  considered.  Boiler 
stays  should  never  be  subjected  to  a  strain  of  more  than  one- 
eighth  of  their  breaking  strength.  The  strength  of  boiler  stays 
may  be  calculated  by  multiplying  the  area  in  inches  between  the 
stays  by  the  pressure  in  pounds  per  square  inch. 

Rule  for  finding  the  strain  allowed  on  a  diagonal  boiler  head 
brace  or  stay  ;  also  rule  for  finding  the  number  of  stays  required 
for  a  certain  size  crown  sheet. 

A  —  Iron  stays  should  not  be  subjected  to  a  greater  stress  than 
from  7,000  to  9,000  pounds  per  square  inch  of  section,  and  if 
they  are  located  obliquely,  the  diameter  will  need  to  be  increased 
an  amount  that  depends  on  the  angle  of  the  stay  to  the  shell. 
Find  the  area  in  square  inches  to  be  supported  by  the  stay,  and 
multiply  it  by  the  pressure  per  square  inch,  multiply  the  product 
by  the  length  of  the  diagonal  stay,  and  divide  the  result  by  the 
perpendicular  length  from  the  flat  surface  to  the  end  of  the  stay. 
The  quotient  will  be  the  stress  on  the  stay,  and  to  obtain  the 
diameter,  divide  the  stress  by  the  allowable  stress  per  square  inch 

of  section,  and  the  quotient 


by  .7854.  The  square  root  of 
the  last  quotient  will  be  the 
diameter  of  the  stay. 

Thus,  in  the  accompanying 
diagram,  we  wish  to  find  the 
diameter  of  the  diagonal- stay 
which    supports  an  area  0"  x  8"  or  48  square  inches.     The 


476  HANDBOOK    ON    ENGINEERING. 

length  of  the  stay  is  25",  and  the  perpendicular  distance  be- 
tween the  stayed  surface  and  the  end  of  the  stay  is  24.148". 
The  boiler  pressure  is  100  pounds  gauge,  so  that  the 
pressure  on  the  surface  supported  will  be  48  x  100  or  4,800 
pounds.  We  multiply  4,800  by  25  and  divide  the  product  by 
24.148",  which  gives  4,970,  nearly.  The  quotient  of  4,970, 
divided  by  7,000  equals  .71;  .71,  divided  by  .7854  equals 
.9039,  and  the  square  root  of  this  is  .95  or  .95",  the  diameter  of 
a  stay  that  will  support  48  square  inches  in  the  position  shown. 

A  convenient  formula  for  finding  the  diameter  of  oblique  stays 
is, 

\~A~P 
D  equals  1.  !•>.»" 

\L  cos# 

D  equals  diameter  of  the  stay. 

A       "       area  in  square  inches  to  be  supported. 

P      "       pressure,  per  square  inch. 

L       "       safe  load  per  square  inch  of  stay  section. 

B       "       angle  between  the  shell  and  the  stay. 

Using"  the  preceding  problem  as  an  example  and  referring  to 
the  same  diagram,  we  have  angle  B  equal  to  15°,  and  all  the  other 
dimensions  as  previously  given.  Therefore, 


equals 


7000  X  .96593 

The  diameter  of  the  stay,  when  the  above  is  simplified,  is 
.9526",  or  practically  1".  A  rule  for  finding  the  pitch  of  stays 
for  any  flat  surface  is  given  below. 

J.  A  safe  formula  for  the  strength  of  stayed  fiat  surfaces  is 
that  given  by  Unwin's  machine  design.  When  the  spacing  of 
the  stays  is  desired,  assuming  that  it  is  the  same  in  each  direc- 
tion, we  have, 


a  equals  8  t 


\2p 


HANDBOOK    ON    ENGINEERING.  477 

where  a  equals  spacing  of  stays  or  rivets  in  inches,/  equals  safe 
working  strength  of  the  plate,  t  equals  thickness  of  plate,  and  p 
equals  boiler  pressure.  Expressed  as  a  rule,  this  reads :  Divide 
the  safe  strength  of  the  plate  by  twice  the  pressure ;  extract  the 
square  root  of  the  quotient  and  multiply  the  final  result  by  three 
times  the  thickness  of  the  plate.  The  result  will  be  the  spacing 
of  the  stays  in  inches.  For  example,  boiler  pressure  100  pounds, 
plate  1/2  inch  thick,  safe  strength  of  plate,  10,000  pounds  per 
square  inch  ;  2p  equals  2  x  100  equals  200  ;  f/2p  equals  10000/200 
equals  50;  V  50  equals  7.07;  ot  equals  3/2  equals  1-1/2  equals 
1.5;  7. 07  x  1.5  equals  10.0  for  the  spacing.  In  making  such  a 
calculation  care  must  be  exercised  not  to  assume  too  high  values 
for  the  strength  of  the  plate.  It  is  not  safe  to  count  on  more 
than  (50,000  pounds  for  the  strength  of  steel  plates  and  40,000 
for  iron .  The  working  strength  must  be  taken  not  higher  than  1/6 
of  this,  or  10,000  for  steel  and  6,666  for  iron,  and  lower  values 
still  would  be  better,  say  (J,000  for  steel  and  6,000  for  iron. 

2*  The  safe  pressure  for  a  boiler  to  carry,  so  far  as  the 
flat,  stayed  surfaces  are  concerned,  may  be  found  from  the 
above  formula  by  transposing  it  a  little,  as  follows:  — 

9  f2  f 
p  equals  ~^T 

Now,  applying  this  to  the  above  example,  we  have  p  equals 
9  x.52  x  10000  9  x  .25  x  10000 

~l&xTlOL25~~  6q  2x110.25  after   re~ 

22500 

duction  equals  equals  102,  or  substantially  the  pressure 

Z  ZO  ,<D(j 

assumed  in  the  iirst  example. 

RIVETED  AND  LAP  WELDED  FLUES. 

The  following  table  shall  include  all  riveted  and  lap-welded 
flues  exceeding  6  inches  in  diameter  and  not  exceeding  40  inches 
in  diameter  not  otherwise  provided  by  law,  as  required  by  U.  S.  Gov, 


478 


HANDBOOK    ON    ENGINEERING. 


^egefskk8«ssssi|28»i2S^a 

Thickness  of  material 
required. 

H 

3 

3 
M 

*d 
g 

I 

i 

I-; 
§ 

1 

i 
i 

I- 
2 

s>ooooonoooooo«ooo5ooooo 

aJ'C  O 
ta  *-•  >~>  *^  O  f*  g 

Over  6  and 
not  over  7 
inches. 

E 
o 

0 

O 

a 
1 

Is 

Is 
Is 

Least  thickness 
allowab 

Greatest  length  of  sections 
allowable,  5  feet. 

::..::      :  :  .  :      :  :  :  :                 :  :  9^ 

Over  7  and 
not  over  8 
inches. 

................  ^g^S.  .  p.g] 

.........                       .  .         ^ 

Over  8  and 
not  over  9 
inches. 

'••'•••••      •      •      '      *       '  .40 

of  material 
le. 

:     :     <BT3^ 

Over  9  and 
not  over  10 
inches. 

::::-::.:::::  £g£g£3£:  .  :  ggs 

-.-.a. 

'  :  •      '.''.'.'.'.'.'.                     '     '  '        "-Q 

Over  10  and 
not  over  11 
inches. 

h 

Least  thickness  of  material  allowable. 

C 

1 

5T 

B 

a* 
o 

1 
o' 
o 

00 

cT 

P 

cr 

::::.:::::.   g||Sg§:         =  SS| 

'  i  ::::::.:*::                    :      :  i  *   '  f^ 

Over  11  and 
not  over  12 
Inches. 

h 

::::::     :  :  :  :  K>  •*  -.-,-,-.  ~  ^       :  •  3*| 

:::-:•-      '  :  :  '  ^OWOSCDt*J'orj:  •::•*?§. 

.::::'      .  .                             :  :  :  .  .     ^  ^ 

Over  12  aud 
not  over  13 
inches. 

Is 

::;-,•::      :  :  8SS83a8S8:  :  :  :  :  S?  | 

::::::      gg-s---^.-;  :  :  |  |  ;  S|| 

Over  13  and 
not  over  14 
inches. 

I* 

:::;••                                   ::::::•'§• 

i> 

Over  14  and 
not  over  15 
inches. 

Is 
Is 

.   .    .       .                                          5      o 

.  j  :      :  §^gSSS§§2SS:  :  :  :  :  :  :  |l| 

:  :  .                                     .:.:::.:  ^^  ^ 

Over  15  and 
not  over  16 
inches. 

:  :  :      issSS^SgHsiii:  :  :  :  :  :  :  :  32  » 

•  :  :                                        :::::•:;••§• 

:  :  :     -                           ::::;::::  g-g^ 

Over  16  and 
not  over  17 
inches. 

Is 

.  j  ;  ?,£^32%$&t%l  :;::::::«?| 

:  :                                  ::.::::..  a^^ 

Over  17  and 
not  over  18 
inches. 

Is 

.  ;  tta^3848«6«K:  ;     :  ;  ;  ;  :  |  ;  3?| 

:  .-a^^^^,^^,.,^^,-:  :  •     :::::::  gg| 

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HANDBOOK    ON    ENGINEERING, 


479 


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480  HANDBOOK    ON    KN<!  I  NKKKI  \(  J . 

For  any  flue  requiring-  more  pressure  thuu  is  given  in  table,  the 
same  will  be  determined  by  proportion  of  thickness  to  any  given 
pressure  in  table  to  thickness  for  pressure  required,  as  per  exam- 
ple :  A  flue  not  over  19  inches  diameter  and  3  feet  long,  requires 
a  thickness  of  .39  of  an  inch  for  176  pounds  pressure;  what 
thickness  would  be  required  for  250  Ibs.  pounds  pressure? 

176:  .139::    250:    .5539, 
or  a  thickness  of  .554  inch. 

Or,  if  .39  inch  thickness  gives  a  pressure  of  176  Ibs.,  what  will 
.554  inch  thickness  give? 

.39  :    176  :  :    .554  :  250  pounds  required. 

And  all  such  flues  shall  be  made  in  sections,  according  to  their 
respective  diameters,  not  to  exceed  the  lengths  prescribed  in  the 
table  and  such  sections  shall  be  properly  fitted  one  into  the  other 
and  substantially  riveted,  and  the  thickness  of  material  required 
for  any  such  flue  of  any  given  diameter  shall  in  no  case  be  less  than 
the  least  thickness  prescribed  in  the  table  for  any  such  given 
diameter ;  and  all  such  flues  may  be  allowed  the  prescribed  work- 
ing steam  pressure,  if  in  the  opinion  of  the  inspectors,  it  is 
deemed  safe  to  make  such  allowance.  And  inspectors  are  there- 
fore required,  from  actual  measurement  of  each  flue,  to  make 
such  reduction  from  the  prescribed  working  steam  pressure  for 
any  material  deviation  in  the  uniformity  of  the  thickness  of  the 
material,  or  for  any  material  deviation  in  the  form  of  the  flue  from 
that  of  a  true  circle;  as  in  their  judgment  the  safety  of  navigation 
may  require. 

Riveted  and  lap-welded  flues  of  any  thickness  of  material, 
diameter,  and  length  of  sections  prescribed  in  the  table,  may  be 
made  in  sections  of  any  desired  length,  exceeding  the  maximum 
length  allowed  by  the  table,  by  reducing  the  prescribed  pressure 


HANDBOOK    ON    ENGINEERING.  481 

in  proportion  to  the  iiu-i-onscd  length  of  section,  according  to  the 
following  rule :  — 

Rule. —  Multiply  the  pressure  in  the  table  allowed  for  any  pre- 
scribed thickness  of  material  and  diameter  of  flue  by  the  greatest 
length,  in  feet,  of  sections  allowable  for  such  flue,  and  divide  the 
product  by  the  desired  length  of  sections,  in  feet,  from  center  line 
to  center  line  of  rivets,  in  the  circular  seams  of  such  sections,  and 
the  quotient  will  give  the  working  steam  pressure  allowable. 

Example*  —  Taking  a  flue  in  the  table  24  inches  in  diameter, 
required  to  be  made  in  sections  not  exceeding  2.5  feet  in  length, 
and  having  a  thickness  of  material  of  .44  of  an  inch,  and  allowed 
a  pressure  of  157  Ibs.,  and  it  is  desired  to  make  this  flue  in  sec- 
tions 5  feet  in  length. 

Then  we  have 

157  x2.5 

_ =j=s  <8.5  Ibs.  pressure  allowable. 

5 

THICKNESS  OF  MATERIAL  REQUIRED  FOR  TUBES  AND  FLUES 
NOT  OTHERWISE  PROVIDED  FOR. 

Tubes  and  flues  not  exceeding  6  inches  in  diameter,  and  made 
of  any  required  length  ;  and 

Lap-welded  flues  required  to  carry  a  working  steam  pressure  not 
to  exceed  60  Ibs.  per  square  inch,  and  having  a  diameter  not 
exceding  16  inches,  and  a  length  not  exceeding  18  feet ;  and 

Lap-welded  flues  required  to  carry  a  steam  pressure  exceeding 
60  Ibs.  per  square  inch,  and  not  exceeding  120  Ibs.  per  square 
inch,  and  having  a  diameter  not  exceeding  16  inches  and  a 
length  not  exceeding  18  feet,  and  made  in  sections  not  exceeding 
5  feet  in  length,  and  fitted  properly  one  into  the  other,  and  sub- 
stantially riveted ;  and 

All  such  flues  shall  have  a  thickness  of  material  according 
to  their  respective  diameters,  as  prescribed  in  the  following 

table :  — 

31 


482 


HANDBOOK    OX    ENGINEERING. 


Outside 
diameter. 

Thickness. 

Outside 
diameter. 

Thickness. 

,;-;::,^;,  *  •***. 

i 

Inches. 

Inch. 

IncJicfi. 

tncli. 

1 

Inches.             Trick. 

1 

.072 

34 

.120 

9 

.180 

I*' 

.072 

3* 

.120 

10 

.203 

14 

.083 

31 

.120 

11 

.220 

ii 

.095 

4 

.134 

12 

.229 

2 

.095 

44 

.134 

13 

.238 

24 

.095 

5 

.148 

14 

.24* 

*i 

.109 

(> 

.1(55 

15 

.2T)9 

n 

.109 

i 

.165 

16 

.270 

3 

.109 

8 

.165 

1 

Tubes,  water  pipes  and  steams  pipes,  made  of  steel  manufac- 
tured by  the  Bessemer  process,  may  be  used  in  any  marine  boiler 
when  the  material  Irom  which  pipes  are  made  does  not  contain 
more  than  .06  percent  of  phosphorus  and  .04  per  cent  of  sulphur, 
to  be  determined  by  analysis  by  the  manufacturers,  verified  by 
them,  and  copy  furnished  the  user  for  each  order  tested ;  which 
analysis  shall,  if  deemed  expedient  by  the  Supervising  Inspector- 
G-eneral,  be  verified  by  an  outside  test  at  the  expense  of  the 
manufacturer  of  the  tubes  or  pipes.  No  tube  increased  in  thick- 
ness by  welding  one  tube  inside  of  another,  shall  be  allowed 
for  use. 

Seamless  copper  or  brass  tubes,  not  exceeding  three-fourths  of 
an  inch  in  diameter,  may.be  used  in  the  construction  of  water 
tube  pipe  boilers  or  generators,  when  liquid  fuel  is  used.  There 
may  also  be  used  in  their  construction  copper  or  brass  steam 
drums,  not  exceeding  14  inches  in  diameter,  of  a  thickness  of 
material  not  less  than  five-eighths  of  an  inch,  and  copper  or  brass 
steam  drums  12  inches  in  diameter  and  under,  having  a  thickness 
of  material  not  less  than  one-half  inch.  All  the  tubes  and  drums 
referred  to  in  this  paragraph  shall  be  made  from  ingots  or  blanks 
drawn  down  to  size  without  a  seam.  Water-tube  boilers  or  gen- 


HANDBOOK    ON    ENGINEERING.  483 

erators  so  constructed  may  be  used  for  marine  purposes  with 
oone  other  than  liquid  fuel. 

Lap-welded  Hues  not  exceeding  0  inches  in  diameter  may  be 
made  of  any  required  length  without  being  made  in  sections. 
And  till  such  lap-welded  flues  and  riveted  flues  not  exceeding  6 
inches  in  diameter  may  be  allowed  a  working  steam  pressure  not 
to  exceed  225  Ibs.  per  square  inch,  if  deemed  safe  by  the 
inspectors. 

Lap- welded  Hues  exceeding  0  inches  in  diameter  and  not 
exceeding  10  inches  in  diameter,  and  not  exceeding  18  feet  in 
length,  and  required  to  carry  a  steam  pressure  not  exceeding 
60  Ibs.  per  square  inch,  shall  not  be  required  to  be  made  in 
sections. 

Lap-welded  ^ud  riveted  flues  exceeding  0  inches  in  diameter 
and  not  exceeding  10  inches  in  diameter,  and  not  exceeding  18 
feet  in  length,  and  required  to  carry  a  steam  pressure  exceeding 
00  Ibs.  per  square  inch,  and  not  exceeding  120  Ibs.  per  square 
inch,  may  be  allowed,  if  made  in  sections  not  exceeding  5  feet  in 
length  and  properly  fitted  one  into  the  other,  and  substantially 
riveted. 

On  all  boilers  built  after  July  1st,  181)0,  a  bronze  or  brass- 
seated  stop-cock  or  valve  shall  be  attached  to  the  boiler  between 
all  check  valves  and  all  steam  and  feed  pipes  and  boilers,  in  order 
to  facilitate  access  to  connections.  Where  such  cocks  or  valves 
exceed  1£  inches  in  diameter,  they  must  be  flanged  to  boiler. 
The  stop-valves  attached  to  main  -steam-pipes  may,  however,  be 
made  of  cast-iron  or  other  suitable  material.  The  date  referred 
to  above  applies  to  this  paragraph  only. 

All  copper  steam-pipes  shall  be  flanged  to  a  depth  of  not  less 
than  four  times  the  thickness  of  the  material  in  the  pipes,  and  all 
such  flanging  shall  be  made  to  a  radius  not  to  exceed  the  thickness 
of  the  material  in  such  pipes.  And  all  such  pipes  shall  have  a 
thickness  of  material  according  to  the  working  steam  pressure 


484  HANDBOOK    ON    ENGINEERING. 

allowed,  and  such  thickness  of   material   shall   be    determined  bv 
the  following  rule  :  — 

Rule* — Multiply  the  working  steam  pressure  in  pounds  per 
square  inch  allowed  the  boiler  by  the  diameter  of  the  pipe  in 
inches,  then  divide  the  product  by  the  constant  whole  number 
8000,  and  add  .0625  to  the  quotient;  the  sum  will  give  the  thick- 
ness of  the  material  required. 

Example*  —  Let  175  Ibs.  —  working  steam  pressure  per  square 
inch  allowed  the  boiler, 

5  inches  =  diameter  of  the  pipe, 

8000  —  a  constant. 
Then  we  have  :  — 

-f-  .0625  =  .1718  -f-  thickness  of  material  in  decimals  of 
oOOO 

an  inch. 

The  llanges  of  all  copper  steam  pipes  over  three  inches  in 
diameter  shall  be  made  of  bronze  or  brass  composition,  and 
shall  have  a  thickness  of  material  of  not  less  than  four  times 
the  thickness  of  material  in  the  pipes  plus  .25  of  an  inch ;  and 
all  such  flanges  shall  have  a  boss  of  sufficient  thickness  of 
material  projecting  from  the  back  of  the  flange  a  distance  of 
not  less  than  three  times  the  thickness  of  material  in  the  pipe ; 
and  all  such  flanges  shall  be  counter-bored  in  the  face  to  lit  the 
flange  of  the  pipe ;  and  the  joints  of  all  copper  steam  pipes 
shall  be  made  with  a  sufficient  number  of  good  and  substantial 
bolts  to  make  such  joints  at  least  equal  in  strength  to  all  other 
parts  of  the  pipe. 

The  terminal  and  intermediate  joints  of  all  wrought  iron  and 
homogeneous  steel  feed  and  steam  pipes  over  2  inches  in  diameter 
and  not  over  5  inches  in  diameter,  other  than  on  pipe  or  coil 
boilers  or  steam  generators,  shall  be  made  of  wrought  iron,  homo- 
geneous steel,  or  malleable  iron  flanges,  or  equivalent  material ; 
and  all  such  flanges  shall  have  a  depth  through  the  bore  of  not 


HAM  >n<><  >K    ON    KNGIXKKIMNG.  -IS.") 

less  than  that  equal  to  one-half  of  the  diameter  of  the  pipe  to  which 
any  such  flange  may  be  attached  ;  and  such  bores  shall  taper 
slightly  outwardly  toward  the  face  of  the  flanges  ;  and  the  OIK  Is 
of  such  pipes  shall  be  enlarged  to  lit  the  bore  of  the  ilanges,  and 
they  shall  be  substantially  beaded  into  a  recess  in  the  face  of  each 
flange.  But  where  such  pipes  are  made  of  extra  heavy  lap-welded 
steam  pipe,  the  Ilanges  may  be  attached  with  screw  threads  ;  and 
all  joints  in  bends  may  be  made  with  good  and  substantial 
malleable  iron  elbows,  or  equivalent  material. 

All  feed  and  steam  pipes  not  over  2  inches  in  diameter  may 
be  attached  at  their  terminals  and  intermediate  'joints  with  screw 
threads  by  Ilanges,  sleeves,  elbows,  or  union  couplings  ;  but 
where  the  ends  of  such  pipes  at  their  terminal  joints  are  screwed 
into  material  in  the  boiler,  drum  or  other  connection  having  a 
thickness  of  not  less  than  ]  inch,  the  flanges  of  such  terminal 
joints  may  be  dispensed  with.  Where  any  such  pipes  are  not 
over  one  inch  in  diameter  and  any  of  the  terminal  ends  are  to  be 
attached  to  material  in  the  boiler  or  connection  having  a  thickness 
of  less  than  i  inch,  a  nipple  shall  be  firmly  screwed  into  the 
boiler  or  connection  against  a  shoulder,  and  such  pipe  shall  be 
screwed  firmly  into  such  nipple.  And  should  inspectors  deem  it 
necessary  for  safety,  they  may  require  a  jam  nut  to  be  screwed 
onto  the  inner  end  of  any  such  nipple. 

The  word  '  '  terminal  '  '  shall  be  interpreted  to  mean  the  points 
where  steam  or  feed  pipes  are  attached  to  such  appliances  on 
boilers,  generators  or  engine,  as  are  placed  on  such  to  receive 
them  . 

All  lap-welded  iron  or  steel  steam-pipes  over  5  inches  in  diam- 
eter, or  riveted  wrought-iron  or  steel  steam-pipes  over  5  inches  in 
diameter,  in  addition  to  being  expanded  into  tapered  holes  and 
substantially  beaded  into  recess  in  face  of  flanges,  as  provided  in 
preceding  paragraph  for  steam  and  feed-pipes  exceeding  2  inches 
and  not  exceeding  5  inches  in  diameter,  shall  be  substantially  and 


/ 


486 


HANDBOOK    ON    ENGINEERING. 


firmly  riveted,  with  good  and  substantial  rivets,  through  the  hubs 
of  such  flanges  ;  and  no  such  hubs  shall  project  from  such  flanges 
less  than  2  inches  in  any  case. 

Steam-pipes  of  iron  or  steel,  when  lap- welded  by  hand  or 
machine,  with  their  flanges  welded  on,  shall  be  tested  to  a  hydro- 
static pressure  of  at  least  double  the  working  pressure  of  the 
steam  to  be  carried  and  properly  aiinealed  after  all  the  work 
requiring  fire  is  finished.  When  an  affidavit  of  the  manufacturer 
is  furnished  that  such  test  has  been  made  and  annealed,  they  may 
be  used  for  marine  purposes. 

WROUGHT    IRON    WELDED    PIPE. 

DIMENSIONS,    WEIGHTS,    ETC.,    OF    STANDARD    SIZES  FOR  STEAM,  GAS, 
WATER,    OIL,    ETC. 

1  inch  and  below  are  butt- welded,  and  tested  to  300  pounds 
per  square  inch  hydraulic  pressure. 

li  inch  and  above  are  lap-welded,  and  tested  to  500  pounds 
per  square  inch  hydraulic  pressure. 


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Inch. 

Inches. 

Inches. 

Feet. 

Inches. 

Inches. 

Feet. 

Lbs. 

Lbs 

.40 

1.272 

9.44 

.012 

.129 

2500. 

.24 

27 

.0006* 

005 

.54 

1  .  696 

7.075 

049 

229 

1385. 

.42 

18 

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.021 

.67 

2'  121 

5.657 

.110 

.  358 

751.5 

.56 

18 

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.047 

84 

2.652 

4  502 

.196 

.  554 

472.4 

.84 

14 

.0102 

.085 

1.05 

3.299 

3.637 

.441 

.866 

270. 

1.12 

14 

.0230 

.190 

1 

1  31 

4.134 

2.903 

.785 

1.357 

166.9 

1.67 

114 

.0408- 

.349 

1  66 

5.215 

2.301 

1  227 

2  .  164 

96.25 

2.25 

III 

.0638 

.527 

li 

1.9 

5.969 

2.01 

1.767 

2.835 

70.65 

2.69 

Hi 

.  0918 

.760 

2* 

2.37 

7.461 

1.611 

3  141 

4.430 

42.36 

8.66 

ll| 

.1632 

1.356 

2.87 

9.032 

1.328 

4  908 

6.491 

30.11 

5.77 

8 

.2550 

2.116 

35 

3  5 

10.996 

1  091 

7.068 

9.621 

19.49 

7.54 

8 

.3673 

3.049 

3* 

4. 

12.566 

.955 

9.621 

12.566 

14.56 

9.05 

8 

.4998 

4-155 

4 

4.5 

14.137 

.849 

12.566 

15.904 

11.31 

10.72 

8 

.6528 

5.405 

4* 

5. 

15.708 

.765 

15.904 

19.635 

9.03 

12.49 

8 

.8263 

6.851 

5 

5.56 

17.475 

.629 

19.635 

24.299 

7.20 

14.56 

8 

1.020 

8.500 

6 

6.62 

20.813 

.577 

28.274 

34.471 

4.98 

18.76 

8 

1.469 

12.312 

7 

7.62 

23  954 

.505 

38.484 

45.663 

3.72 

23.41 

8 

1.999 

16.662 

8 

8  62 

27.096 

.444 

50.265 

58.426 

2.88 

28.34 

8 

2.611 

21.750 

9 

9  68 

30.433 

.394 

63.617 

73.715 

2.26 

34.67 

8 

3.300 

27.500 

10 

10.75 

33.772 

.355 

78.540 

90  792 

1.80 

40.64 

8        4.081        34.000 

ANDHOOK    o\    ENGINEERING. 


487 


PULSATION  IN  STRAfl-BOILERS. 

Pulsation  i'1  steam-boilers,  though  not  discernible  to  the  eye, 
as  in  animated  nature,  goes  on  intermittently  in  some  boilers 
whenever  they  are  in  use.  It  is  induced  by  weakness  and  want 
of  capacity  in  the  boiler  to  supply  the  necessary  quantity  of 
steam,  and  sometimes  is  caused  by  the  boiler  being  badly  de- 
signed, thereby  admitting  of  a  great  disproportion  between  the 
heating-surface  and  steam-room.  Boilers  are  frequently  found  in 
factories  that  were  originally  not  more  than  of  sufficient  capacity 
to  furnish  the  necessary  quantity  of  steam,  but,  as  business 
increased,  it  became  necessary  to  increase  the  pressure  and  also 
the  speed  of  the  engine;  or,  perhaps  to  replace  it  with  a  larger 
one,  which  has  to  be  supplied  with  steam  from  the  same  boiler.. 
The  result  is,  each  time  the  valve  opens  to  admit  steam  to  the 
cylinder,  about  one-third  of  the  whole  quantity  in  the  boiler  is 
admitted,  thus  lowering  the  pressure  ;  the  next  instant,  under  the 
influence  of  hard  firing,  or,  perhaps,  a  forced  draught,  the  steam 
is  brought  to  the  former  pressure,  and  so  on  ;  this  lessening  and 
increasing  the  pressure  continues  while  the  engine  is  in  motion, 
which  has  an  effect  on  the  boiler  similar  to  the  breathing  of  an 
animal. 

Trie  strains  induced  by  this  pulsation  are  transmitted  to  the 
weakest  places,  viz.,  the  line  of  the  rivet  holes,  and  that  marked 

by  the  tool  in  the  process  of 
calking  ;  the  result  is,  the  plate 
is  broken  in  two,  as  shown  in 
the  above  cut.  The  manner  in 
which  the  break  takes  place 
may  be  illustrated  by  filing  a 
small  nick,  or  drilling  a  small 
hole,  in  a  piece  of  hoop  or  band- 
iron,  and  then  bending  back 


488 


HANDBOOK    OX    ENGINEERING. 


and  forth,  when  it  will  be  discovered  that  the  material  will  break 
just  at  that  point,  however  slight  the  nick  or  small  the  hole  may 
be.  Pulsation  is  frequently  very  severe  in  the  boilers  of  tug- 
boats when  commencing  to  start  a  heavy  tow,  and  also  in  loco- 
motives when  starting  long  trains.  Some  frightful  explosions  of 
the  boilers  of  tug-boats  and  locomotives  have  occurred  under 
such  circumstances.  Pulsation,  if  permitted  to  continue,  is  sure 
to  effect  the  destruction  of  the  boiler.  It  is  always  made  mani- 
fest by  the  vibrations  of  the  pointers  on  steam  gauges,  or  an 
unsteadiness  in  the  mercury  column.  It  may  be  remedied,  to  a 
certain  extent,  by  adding  a  larger  steam  dome,  but  this  has  a 
tendency  to  weaken  the  boiler  and  render  it  more  unsafe.  Tho 
only  sure  preventive  of  such  a  silent  and  destructive  agent  is  to 
have  the  boiler  of  sufficient  capacity  in  the  first  place. 


WEIGHT    OP    SQUARE    AND    ROUND    IRON    PER    LINEAR    FOOT. 


SIDE 
OK 
DIAM. 

Weight, 
Square. 

Weight, 
Round. 

SIDE 
OR 
DIAM. 

Weight, 
Square. 

Weight. 
Round. 

SIDE 
OR 
DIAM. 

Weight, 

Siju.-uv. 

Weight, 

Uouinl. 

tV 

.013 

.01 

2 

13.52 

10.616 

5 

84.48 

66.35 

1 

.053 

.041 

* 

15.263 

11.988 

k 

93.168 

73.172 

ft 

.118 

.093 

i 

17.112 

13.44 

h 

102.24 

80.304 

1 

.211 

.165 

1 

19.066 

14.975 

I 

111.756 

87.776 

i 

.475 

.373 

h 

21.12 

16.588 

I 

.845 

.663 

t 

23.292 

18.293 

6 

121.664 

95.552 

1 

1.32 

1.043 

I 

25.56 

20.076 

i 

132.04 

103.704 

* 

1.901 

1.493 

I 

27.939 

21.944 

i 

142.816 

112.16 

I 

2.588 

2.032 

1 

154.012 

120.96 

3 

30.416 

23.888 

i 

3.38 

2.654 

i 

35.704 

28.04 

7 

165.632 

130.048 

1 

4.278 

3.359 

4 

41.408 

32.515 

\ 

177.672 

139.544 

5.28 

4.147 

t 

47.534 

37.332 

h 

190.136 

149.328 

| 

G.39 

5.019 

3 

203.024 

1  of).  456 

h 

7.604 

5.972 

4 

54.084 

42.464 

I 

8.926 

7.01 

1 

61.055 

47.952 

8 

216.336 

169.856 

i 

10.352 

8.128 

I 

68.448 

53.76 

1 

11.883 

9333 

3 

76.264 

59.9 

9 

273.792 

215.04 

HANDBOOK    ON    ENGINEERING.  489 

WATER  COLUHNS. 

Every  boiler  should  be  equipped  with  a  safety  water  column. 
Next  to  keeping  the  steam  pressure  within  the  limits  of  safety, 
the  most  important  point  to  be  observed  in  operating  steam  boilers 
is  the  maintenance  of  the  proper  water  level.  If  the  water  level 
is  too  low,  there  is  danger  of  burning  the  tubes  and  plates  and? 
perhaps,  of  wrecking  the  boiler  ;  if  it  is  too  high,  water  is  liable  to 
be  carried  along  with  the  steam  and  cause  damage  in  the  engine, 
while  a  constant  variation  in  the  water  level  produces  a  waste  of  fuel 
and  unsteady  pressure,  and  impairs  the  life  of  the  boiler.  Safety 
water  columns  have  been  devised  for  the  purpose  of  insuring  owners 
of  steam  boilers  against  accidents  of  this  kind.  They  are  so  ar- 
ranged that  any  variation  in  the  water  level  beyond  reasonable  lim- 
its will  be  loudly  proclaimed  by  means  of  a  suitable  steam  whistle. 

STEAM-GAUGES. 

The  object  of  the  steam-gauge  is  to  indicate  the  steam  pressure 
in  the  boiler,  in  order  that  it  may  not  be  increased  far  above  that 
at  which  the  boiler  was  originally  considered  safe  ;  and  it  is  as  a 
provision  against  this  contingency  that  a  really  good  gauge  is  a 
necessity  where  steam  is  employed,  for  no  guide  at  all  is  vastly 
better  than  a  false  one.  The  most  essential  requisites  of  a  good 
steam-gauge  are,  that  it  be  accurately  graduated,  and  that  the 
material  and  workmanship  be  such  that  no  sensible  deterioration 
may  take  place  in  the  course  of  its  ordinary  use.  The  pecuniary 
loss  arising  from  any  considerable  iluctuation  of  the  pressure  of 
steam  has  never  been  properly  considered  by  the  proprietors  of 
engines.  If  steam  be  carried  too  high,  the  surplus  will  escape 
through  the  safety-valve,  and  all  the  fuel  consumed  to  produce 
such  excess  is  so  much  dead  loss.  On  the  other  hand,  if  there  be 
at  any  [time  too  little  steam,  the  engine  will  run  too  slow,  antf. 
every  lathe,  loom,  or  other  machine  driven  by  it,  will  lose  its 
speed  and,  of  course,  its  effective  power  in  the  same  pro- 


490  HANDBOOK    ON    .KNiJINEKKIXfJ. 

portion.  A  loss  of  one  revolution  in  ten  at  once  reduces  the  pro- 
ductive power  of  every  machine  driven  by  the  engine  ten  per  cent, 
and  loses  to  the  proprietor  ten  per  cent  of  the  time  of  every 
workman  employed  to  manage  such  machine.  In  short,  the  loss 
of  one  revolution  in  ten  diminishes  the  productive  capacity  of  tin- 
whole  concern  ten  per  cent,  so  long  as  such  reduced  rate  con- 
tinues;  while  the  expenses  of  conducting  the  shop  (rent,  wages, 
insurance,  etc.)  all  run  on  as  if  everything  was  in  full  motion. 
A  variation  to  this  amount  is  a  matter  of  frequent  occurrence, 
and  is,  indeed,  unavoidable,  unless  the  engineer  is  afforded 
facilities  to  prevent  it.  A  very  little  reflection  will  satisfy  any 
one  that  it  must  be  a  very  small  concern,  indeed,  in  which  a  half- 
hour's  continuance  of  it  would  not  produce  a  result  more  than 
enough  to  defray  the  cost  of  a  very  expensive  instrument  to  pre- 
vent it.  If  the  engineer,  to  avoid  this  loss,  keeps  a  surplus  of 
steam  constantly  on  hand,  he  is  constantly  wasting  the  steam, 
and  consequently,  fuel,  thus  incurring  another  loss,  which, 
though  less  alarming  than  the  first,  will  yet  be  serious  and  render 
any  instrument  most  desirable  which  can  prevent  it.  It  is,  there- 
fore, of  great  importance  to  the  proprietors  of  engines  to  have  an 
instrument  which  can  constantly  indicate  the  pressure  in  the 
steam-boilers  with  accuracy.  This  would  enable  the  engineer  to 
keep  his  steam  at  a  constant  pressure,  thus  avoiding  waste  of  fuel 
on  the  one  hand,  and  the  still  more  serious  loss  of  the  productive 
power  of  the  shop  on  the  other.  An  instrument,  therefore,  con- 
stantly indicating  the  pressure  of  steam,  reliable  in  its  character, 
and,  with  ordinary  care,  not  subject  to  derangement,  is  evidently 
a  desideratum  both  to  the  engineer  and  proprietor.  -  The  impor- 
tance of  such  an  instrument,  as  a  preventive  of  explosion,  and  of 
the  frightful  consequences  to  life  and  limb  and  ruinous  pecuniary 
results  of  such  disaster,  is  obvious  on  the  slightest  consideration  : 
but  the  value  of  the  instrument,  in  the  economical  results  of  its 
daily  use,  is  by  no  means  properly  appreciated. 


HANDBOOK  ON  E\<!1\EKKIX(.J .  491 

SAFETY=VALVES. 

The  form  and  construction  of  this  indispensable  adjunct  to  the 
steam  boiler  are  of  the  highest  importance,  not  only  for  the  pres- 
ervation of  life  and  property,  which  would,  in  the  absence  of  that 
means  of  "  safety  "  be  constantly  jeopardized,  but  also  to  secure 
the  durability  of  the  steam-boiler  itself.  And  yet,  judging  from 
the  manner  in  which  many  things  called  safety-valves  have  been 
constructed  of  late  years,  it  would  appear  that  the  true  principle 
by  which  safety  is  sought  to  be  secured  by  this  most  valuable  ad- 
junct is  either  not  well  understood,  or  is  disregarded  by  many 
engineers  and  boiler-makers. 

Boiler  explosions  have  in  many  cases  occurred  when,  to  all 
appearances,  the  safety-valves  attached  have  been  in  good  work- 
ing order ;  and  coroners'  juries  have  not  unfrequently  been 
puzzled,  and  sometimes  guided  to  erroneous  verdicts  by  scientific 
evidence  adduced  before  them,  tending  to  show  that  nothing  was 
wrong  with  the  safety-valves,  and  that  the  devastating  catastro- 
phies  could  not  have  resulted  from  overpressure,  because  in  such 
case  the  safety-valve  would  have  prevented  them.  It  is  supposed 
that  a  gradually  increasing  pressure  can  never  take  place  if  the 
safety-valve  is  rightly  proportioned  and  in  good  working  order. 
Upon  this  assumption,  universally  acquiesced  in,  when  there  is  no 
accountable  cause,  explosions  are  attributed  to  the  "  sticking  " 
of  the  valves,  or  to  "bent"  valve-stems,  or  inoperative  valve- 
springs.  As  the  safety-valve  is  the  sole  reliance,  in  case  of  neg- 
lect or  inattention  on  the  part  of  the  engineer  or  fireman,  it  is 
important  to  examine  its  mode  of  working  closely.  Safety-valves 
are  usually  provided  with  a  spindle  or  guide-pin,  attached  to  the 
under  side,  and  passing  through  a  cross-bar  within  the  boiler, 
directly  under  the  seating  of  the  valve,  which  may  be  seen  in 


492  HANDBOOK    OX     KX(!  INKKIM  \<! . 

the  cut  below.  Now,  it  is  evident  that  if  this  guide-pin 
becomes  bent  from  careless  handling,  the  safety-valve  may 
be  rendered  almost  inoperative,  and,  instead  of  releasing  the 
pressure  at  the  point  indicated,  it  will  turn  sideways, 
and  allow  only  a  small  aperture  for  the  escape  of  steam, 
and,  further,  it  will  not  return  perfectly  to  its  seat ; 
hence,  a  leaky  valve  is  the  result,  and  to  overcome  this  difficulty, 
ignorant  engineers  and  firemen  generally  resort  to  extra  weight- 
ing ;  and  it  is  not  uncommon  to  find  double  or  treble  the  weight 


corresponding  to  the  pressure  required  in  the  boiler.  Another 
difficulty  is  that  the  safety-valve  levers  sometimes  get  bent,  and 
the  weight,  consequently,  hangs  on  one  side  of  the  true  center ; 
this,  it  will  be  seen,  causes  the  valve  to  rest  more  heavily  on  one 
side  than  on  the  other,  and  the  greater  the  added  weight  the 
greater  the  difficulty.  The  seats  of  safety-valves  should  be 
examined  frequently  to  see  that  no  corrosion  has  commenced  ;  as 
valves,  especially  if  leaky,  become  corroded  and  often  stick  fast, 
so  that  no  little  force  is  required  to  raise  them.  If,  when  a 
safety-valve  is  properly  weighted,  it  should  be  found  leaking,  do 
not  put  on  extra  weights,  but  immediately  make  an  examination, 
and  in  all  probability  the  seat  or  guide-pin  will  be  found  cor- 
roded, or  there  will  be  foreign  matter  between  the  valve  and  its 


HANDBOOK    ON   ENGINEERING. 


493 


seat.  By  taking  the  lever  in  the  hand  and  raising  it  from  its  seat 
a  few  times,  any  substance  that  may  have  kept  it  from  its  seat 
will  be  dislodged ;  or  it  may  turn  out  on  examination  that  the 
lever  had  deviated  from  some  cause  from  a  true  center.  Such 
difficulties  can  be  easily  righted,  but  extra  weight  should  never  be 
added,  as  it  only  aggravates  the  trouble  instead  of  remedying  it. 
When  the  weight  of  the  safety-valve  is  set  on  the  lever  at  safe 
working  pressure,  or  at  the  distance  from  the  fulcrum  necessary 
to  maintain  the  pressure  required  to  work  the  engine,  any 
extra  length  of  lever  should  then  be  cut  off  as  a  precaution, 
to  prevent  the  moving  out  of  the  weight  on  the  lever,  for  the 
purpose  of  increasing  the  pressure,  as,  while  the  lever  remains 
sufficiently  long,  the  weight  can  be  increased  to  a  dangerous 
extent  without  attracting  any  attention ;  while  if  the  lever  is  cut 
off  at  the  point  at  which  the  safe  working  pressure  is  designated, 
any  extra  increase  of  pressure  can  only  be  accomplished  by  add- 
ing more  weight  to  the  lever,  which  is  tolerably  sure  to  attract  the 
attention  of  some  one  interested  in  the  preservation  of  the  lives 
and  property  of  persons  in  the  immediate  vicinity. 

The  bolts  that  form  the  connection  between  the  lever,  fulcrum 
and  valve-stem  should  be  made  of  brass,  in  order  to  prevent  the 
possibility  of  corrosion,  "  sticking  "  or  becoming  magnetized,  as 
it  is  termed  ;  and  for  the  same  reason,  the  valve  and  seat  should 
be  made  of  two  different  metals.  When  safety  valves  become 
leaky  they  should  be  taken  out  and  reground  on  their  seats,  for 
which  purpose  pulverized  glass,  flour  of  emery,  or  the  fine  grit  or 
mud  from  grinding  stone  troughs  are  the  most  suitable  material ; 
but  whether  they  leak  or  not,  they  should  be  taken  apart  at  least 
once  a  year  and  all  the  working  parts  cleaned,  piled  and  read- 
justed. The  safety-valve  is  designed  on  the  assumption  that  it 
will  rise  from  its  seat  under  the  statical  pressure  in  the  boiler, 
when  this  pressure  exceeds  the  exterior  pressure  on  the  valve,  and 
that  it  will  remain  off  its  seat  sufficiently  far  to  permit  all  the 


494  HANDBOOK    ON    ENGINEERING. 

steam  which  the  boiler  can  produce  to  escape  around  the  edges  of 
the  valve.  The  problem  then  to  be  solved  is :  What  amount  of 
opening  is  necessary  for  the  free  escape  of  the  steam  from  the 
boiler  under  a  given  pressure?  The  area  of  a  safety-valve 
is  generally  determined  from  formulae  based  on  the  velocity 
of  the  flow  of  steam  under  different  pressures,  or  upon  the 
results  of  experiments  made  to  ascertain  the  area  necessary  for 
the  escape  of  all  the  steam  a  boiler  could  produce  under  a  given 
pressure.  But  as  the  fact  is  now  generally  recognized  by 
engineers  that  valves  do  not  rise  appreciably  from  their  seats 
under  varying  pressures,  it  is  of  importance  that  in  practice 
the  outlets  round  their  edges  should  be  greater  than  those  based 
on  theoretical  considerations.  The  next  point  to  be  considered  is 
how  high  any  safety  valve  will  rise  under  the  influence  of  a  given 
pressure.  This  question  cannot  be  determined  theoretically,  but 
has  been  settled  conclusively  by  Burg,  of  Vienna,  who  made 
careful  experiments  to  determine  the  actual  rise  of  safety-valves 
above  their  seats.  His  experiments  show  that  the  rise  of  the 
valve  diminishes  rapidly  as  the  pressure  increases. 

TABLE     SHOWING      THE      RISE      OF    SAFETY-VALVES,   IX    PARTS    OF    AN 
INCH,    AT    DIFFERENT    PRESSURES. 

Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs.  Lbs. 


12       20       35       45       50       60       70       80       HO 


T?is 


Taking  ordinary  safety-valves,  the  average  rise  for  pressures 
from  10  to  40  pounds  is  about  J-$  of  an  inch,  from  40  to  70 
pounds  about  g^,  and  from  70  to  90  pounds  about  Ti^  of  an 
inch.  The  following  table  gives  the  result  of  a  series  of  experi- 
ments made  at  the  Novelty  Iron  Works,  New  York,  for  the  pur- 
pose of  determining  the  exact  area  of  opening  necessary  for 


HANDBOOK    ON    ENGINEERING. 


495 


safety-valves,  for  each  square  foot  of  heating  surface,  at  different 
boiler  pressures. 


TABLE. 


•   '-   1.                               =J=  if. 

t<  a        |             a  -  bo 

Xi   O 

XX* 

^  >     . 

"^   w>   fl 

^  >•     .     j                  •"  O  fl 

^   > 

•""5  c 

—  x  i 

-t~ 

^  S  S                          m  S*3 

'SJa  ^ 

«2i 

W*J 

•=t._^'                 W  ^^ 

5  ^  ^                                !     -—  Tl   <* 

S|| 

aq  =s  S 
c«  ^" 

iy 

"H..C 

•   O   nj 

«2 

O     o   . 

'"  rt  o 

"c  .• 

bs-fl 

?fl| 

=*-!     O        •    O 

gg| 

s  a* 

'^£=5 

s  E,"S 

OhHSc2 

O|H£<2 

/.  -_ 

^     .     .'  ^ 

^         Q 

-«      .      .    !H 

"J          * 

..     i    .  IH 

£-5~ 

1?^ 

r*   ^ 

1'^ 

a;  a1  !y^S 

2-S5 
fi 

S^^s 

0.25               .022794 

10 

.005698 

70 

.001015 

0.5                 .021164 

20 

.003221 

80 

.000892 

1                     .018515 

30 

.002244 

90 

.000796 

2 

.014814 

40 

.001723 

100 

.000719 

3                    .012345 

50 

.001398 

150 

.000481 

4                    .010582 

60 

.001176 

200 

.000364 

5                    .009259 

' 

TABLE      OF      COMPARISON     BETWEEN     EXPERIMENTAL      RESULTS      AM) 
THEORETICAL    FORMULAE. 


Boiler  Pressure.  45  pounds. 

Boiler  Pressure,  75  pounds. 

,i.,..,in,rJAreu  of  open- 
BnrfSw       '"K  f»und  by 
1     experiment. 

Area  of  open- 
ing according 
to  formulae. 

Heating 

Surface. 

Area  of  open- 
ing found  by 
experiment. 

Area  of  open- 
ing according 
to  formulae. 

S(|.  Ft.       S(j.  ins.  . 

Sq.  Ins. 

Sq.  Ft. 

Sq.  Ins. 

Sq.  Ins. 

100               .089 

.09 

100 

.12 

.12 

20(1     j          .180 

.19 

200 

.24 

.24 

500     !          .45  • 

.48 

500                 .59 

.59 

1000               .89 

.94 

1000               1.20 

1.18 

2000     '         1.78 

1.90 

2000     i         2.40 

2.37 

5000             4.46 

4.75 

5000              6.00 

5.95 

496  HANDBOOK    ON    ENGINEERING. 

Now,  if  we  compare  the  area  of  openings,  according  to  these 
experiments,  with  Zeuner's  formula,  which  is  entirely  theoretical, 
it  will  be  observed  that  the  results  from  the  two  sources  are 
almost  identical,  or  so  nearly  so  as  not  to'  make  any  material 
difference.  In  the  absence  of  any  generally  recognized  rule,  it 
k>  customary  for  engineers  and  boiler-makers  to  proportion  safety- 
valves  according  to  the  heating  surface,  grate-surface,  or  horse- 
power of  the  boiler.  While  one  allows  one  inch  of  area  of 
safety-valve  to  66  square  feet  of  heating  surface,  another  gives 
one  inch  area  of  safety-valve  to  every  four  horse  power ;  while  a 
third  proportions  his  by  the  grate-surface  —  it  being  the  custom 
in  such  cases  to  allow  one  inch  area  of  safety-valves  to  2  square 
feet  of  grate-surface.  This  latter  proportion  has  been  proved  by 
long  experience  and  a  great  number  of  accurate  experiments,  to 
be  capable  of  admitting  of  a  free  escape  of  steam  without  allowing 
any  material  increase  of  the  pressure  beyond  that  for  which  the 
valve  is  loaded,  even  when  the  fuel  is  of  the  best  quality,  and  the 
consumption  as  high  as  24  pounds  of  coal  per  hour  per  square 
foot  of  grate-surface,  providing,  of  course,  that  all  the  parts  are 
in  good  working  order.  It  is  obvious,  however,  that  no  valve 
can  act  without  a  slight  increase  of  pressure,  as,  in  order  to  lift 
at  all,  the  internal  pressure  must  exceed  the  pressure  due  to  the 
load . 

The  lift  of  safety-valves,  like  all  other  puppet- valves,  de- 
creases as  the  pressure  increases  ;  but  this  seeming  irregularity  is 
but  what  might  be  required  of  an  orifice  to  satisfy  appearances  in 
the  flow  of  fluids,  and  maybe  explained  as  follows:  A  cubic  foot 
of  water  generated  into  steam  at  one  pound  pressure  per  square 
inch  above  the  atmosphere,  will  have  a  volume  of  about  1,600 
cubic  feet.  Steam  at  this  pressure  will  flow  into  the  atmosphere 
with  a  velocity  of  482  feet  per  second.  Now,  suppose  the  steam 
was  generated  in  five  minutes,  or  in  300  seconds,  and  the  area  of 
an  orifice  to  permit  its  escape  as  fast  as  it  is  generated  be  re- 


HANDBOOK    ON    ENGINEERING.  497 

quired,  1600  divided  by  482  x  300  will  give  the  area  of  the  orifice, 
1|-  square  inches.  If  the  same  quantity  of  water  be  generated  into 
steam  at  a  pressure  of  50  pounds  above  the  atmosphere,  it  will 
possess  a  volume  of  440  cubic  feet  and  will  flow  into  the  atmos- 
phere with  a  velocity  of  1791  feet  per  second.  The  area  of  an 
orifice,  to  allow  this  steam  to  escape  in  the  same  time  as  in  the 
first  case,  may  be  found  by  dividing  440  by  1791x300,  the 
result  will  be  ^  square  inches,  or  nearly  -J-  of  a  square  inch,  the 
area  required.  It  is  evident  from  this  that  a  much  less  lift  of  the 
same  valve  will  suffice  to  discharge  the  same  weight  of  steam 
under  a  high  pressure  than  under  a  low  one,  because  the_steam 
under  a  high  pressure  not  only  possesses  a  reduced  volume,  but  a 
greatly  increased  velocity  ;  it  is  also  obvious  from  these  consider- 
ations, that  a  safety-valve,  to  discharge  steam  as  fast  as  the  boiler 
can  generate  it,  should  be  proportioned  for  the  lowest  pressure. 

RULES. 

Rule.  —  Yor  finding  the  weight  necessary  to  put  on  a  safety- 
valve  lever  when  the  area  of  valve,  pressure,  etc.,  are  known : 
Multiply  the  area  of  valve  by  the  pressure  in  pounds  per  square 
inch ;  multiply  this  product  by  the  distance  of  the  valve  from  the 
fulcrum ;  multiply  the  weight  of  the  lever  by  one-half  its  length 
(or  its  center  of  gravity)  ;  then  multiply  the  weight  of  valve  and 
stem  by  their  distance  from  the  fulcrum  ;  add  these  last  two  prod- 
ucts together,  subtract  their  sum  from  the  first  product,  and 
divide  the  remainder  by  the  length  of  the  lever ;  the  quotient  will 
be  the  weight  required. 

EXAMPLE, 

Area  of  valve.  12  in 65          13          8 

Pressure,  (>5  Ibs 12          16          4 

Fulcrum,  4  in.   .     .     .........       780       208       32 


498  HANDBOOK    ON    ENGINEERING. 

Length  of  lever,  32  in 4          13 

Weight  of  lever,  13  Ibs, 


Weight  of  valve  and  stem,  8  Ibs 3120       208 

240          32 


32)2880       240 
90  Ibs. 

Rule  for  finding  the  pressure  per  square  inch  when  the  area  of 
valve,  weight  of  ball,  etc.,  are  known:  Multiply  the  weight  of  ball 
by  length  of  lever,  and  multiply  the  weight  of  lever  by  one-half  its 
length  (or  its  center  of  gravity)  ;  then  multiply  the  weight  of 
valve  and  stem  by  their  distance  from  the  fulcrum.  Add  these 
three  products  together.  This  sum,  divided  by  the  product  of 
the  area  of  valve,  and  its  distance  from  the  fulcrum,  will  give  the 
pressure  in  pounds  per  square  inch. 

EXAMPLE. 

Area  of  valve,  7  in 50          12 

Fulcrum,  3  in 30          15 

Length  of  lever,  30  in 1500        180       18 

Weight  of  lever,  12  Ibs 180 


Weight  of  ball,  50  Ibs.      .      .      .      .      .      .      .          18  7 

Weight  of  valve  and  stem,  6  Ibs 

21)1698  3 

80.85  Ibs.       21 

Rule  for  finding  the  pressure  at  which  a  safety-valve  is 
weighted  when  the  length  of  the  lever,  weight  of  ball,  etc.,  are 
known :  Multiply  the  Jength  of  lever  in  inches  by  the  weight  of 
ball  in  pounds ;  then  multiply  the  area  of  valve  by  its  distance 


HANDKOOK    ON    KNCJINNKKING.  499 

from  the  fulcrum  ;   divide  the  former  product  by  the  latter;  the 
quotient  will  be  the  pressure  in  pounds  per  square  inch. 

EXAMPLE. 

Length  of  lever,  24  in .       52  7 

Weight  of  ball,  52  Ibs.  24 


Fulcrum,  3  in.      .      . 208         21 

Area  of  valve,  7  in 104 

21)1248 

59.42  Ibs. 

The  above  rule,  though  very  simple,  cannot  be  said  to  be 
exactly  correct,  as  it  does  not  take  into  account  the  weight  of  the 
lever,  valve  and  stem. 

Rule  for  finding  center  of  gravity  of  taper  levers  for  safety- 
valves  :  Divide  the  length  of  lever  by  two  (2);  then  divide 
the  length  of  lever  by  six  (6),  and  multiply 'the  latter  quotient 
by  width  of  large  end  of  lever  less  the  width  of  small  end, 
divided  by  width  of  large  end  of  lever  plus  the  width  of  small  end. 
Subtract  this  product  from  the  first  quotient,  and  the  remainder 
will  be  the  distance  in  inches  of  the  center  of  gravity  from  large 
end  of  lever. 

EXAMPLE. 

Length  of  lever 36  in. 

Width  of  lever  at  large  end 3    " 

Width  of  lever  at  small  end 2    " 

36  divided  by  2  =  18  minus   1.2  =  1(5.8  in.     36  divided  by  6  •= 
(I  X  1  —  <>  divided  by  5  =  1.2. 

Center  of  gravity  from  large  end,  16.8  in. 

The  safety-valve  has  not  received  that  attention  from  engi- 
neers and  inventors  which  its  importance  as  a  means  of  safety 


500  HANDBOOK    ON    ENGINEERING . 

so  imperatively  deserves.  In  the  construction  of  most  other 
kinds  of  machinery,  continual  efforts  have  been  made  to  secure 
and  insure  accuracy ;  while  in  the  case  of  the  safety-valve,  very 
little  improvement  has  been  made  either  in  design  or  fitting.  It 
is  difficult  to  see  why  this  should  be  so,  when  it  is  known  that 
deviations  from  exactness,  though  trifling  in  themselves,  when 
multiplied,  not  only  affect  the  free  action  and  reliability  of 
machines,  but  frequently  result  in  serious  injury,  more  partic- 
ularly in  the  case  of  safety-valves. 

Safety-valves  should  never  be  made  with  rigid  stems,  as,  in 
consequence  of  the  frequent  inaccuracy  of  the  other  parts,  the 
valve  is  prevented  from  seating,  thereby  causing  leakage ;  as  a 
remedy  for  which,  through  ignorance  or  want  of  skill,  more 
weight  is  added  on  the  lever,  which  has  a  tendency  to  bend 
the  stem,  thus  rendering  the  valve  a  source  of  danger  instead 
of  a  means  of  safety.  The  stem  should,  in  all  cases,  be  fitted 
to  the  valve  with  a  ball  and  socket  joint,  or  a  tapering  stem 
in  a  straight  hole,  which  will  admit  of  sufficient  vibration  to 
accommodate  the  valve  to  its  seat.  It  is  also  advisable  that 
the  seats  of  safety-valves,  or  the  parts  that  bear,"  should  be  as 
narrow  as  circumstances  will  permit,  as  the  narrower  the  seat 
the  less  liable  the  valve  is  to  leak,  and  the  easier  it  is  to  repair 
when  it  becomes  leaky. 

All  compound  or  complicated  safety-valves  should  be  avoided, 
as  a  safety-valve  is,  in  a  certain  sense,  like  a  clock  —  any 
complication  of  its  parts  has  a  tendency  to  affect  its  reliability 
and  impair  its  accuracy. 

It  has  been  too  much  the  custom  heretofore  for  owners  of  steam 
boilers  to  disregard  the  advice  and  suggestions  of  their  own  en= 
giueers  and  firemen,  even  though  men  of  intelligence  and  experi- 
ence, and  to  be  governed  entirely  by  the  advice  of  self-styled 
experts  and  visionary  theorists. 


HANDBOOK   ON   ENGINEERING.  501 

Table  of  Heating  Surface  in  Square  Feet, 


Diam.  of  Boiler  in  inches 

» 

24 

30 

32 

34 

36 

38 

40 

42 

44 

48 

5  Heating  surface  of  shell 
per  foot  of  length. 

4.19 

5.24 

5.57 

5.93 

6.28 

6.63 

6.98 

7.73 

7.68 

8.38 

Diameter  of  Tube  or  Flue 
in  inches. 

2 

24 

3 

3* 

4 

44 

5 

G 

7 

8 

Whole   External  Heating 
surface  per  foot  length. 

.524 

.655 

.785 

.916 

1.05 

1.18 

1.31 

1.57 

1.83 

2.09 

50 

52 

54 

5G 

58 

60 

62 

64 

66 

68 

70 

72 

8.73 

9.08 

9.42 

9.77 

10.12 

10.47 

10.82 

11.17 

11.52 

11.87 

12.22 

12.57 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

2.36 

2.C2 

2.88 

3.14 

3.40 

3.66 

3.93 

4.19 

4.45 

4.71 

4.96 

5.24 

CENTRIFUGAL  FORCE. 

The  centrifugal  force  of  a  body  depends  upon  its  weight  W  in 
pounds  ;  distance  R  in  feet  it  is  from  the  center  of  rotation,  and 
the  number  of  revolutions  N  it  makes  about  that  center  each 


WR  N* 


minute  and  equals 


Multiply  the  weight  in  pounds  by  radius  in  feet,  by  square 
of  number  of  revolutions,  and  divide  by  2933  =  centrifugal  force 
in  pounds. 


502  HANDBOOK    ON    ENGINEERING. 


CHAPTER     XVIII. 
THE  WATER  TUBE  SECTIONAL  BOILER. 

The  water  tube  sectional  boiler  has  been  a  growth  of  many 
years  and  of  many  different  minds.  There  are  some  two  and  a 
half  million  horse-power  in  daily  service  in  the  United  States 
alone,  and  the  number  is  rapidly  increasing.  Large  orders  for 
this  type  of  boiler  have  often  been  repeated,  adding  proof  that  its 
principles  are  correct  and  appreciated  by  those  having  them  in 
use  and  in  charge.  This  being  the  case,  purchasers  should  note 
well  the  points  of  difference  in  the  various  water  tube  boilers 
claiming  their  attention,  and  particularly  see  that  the  claims 
made  for  them  are  embodied  in  their  actual  construction.  The 
general  principles  of  construction  and  operation  of  this  class  of 
steam  boilers  are  now  well  known  to  engineers  and  steam  users. 
In  selecting  a  water  tube  boiler  there  are  several  vital  points  to 
be  considered :  — 

1st.  Straight  and  smooth  passages  through  the  headers  of  ample 
area,  insuring  rapid  and  uninterrupted  circulation  of  the  water. 

2d.  The  baffling  of  the  gases  (without  throttling  or  impeding 
the  circulation  of  the  water)  in  such  a  way  that  they  are  com- 
pelled to  pass  over  every  portion  of  the  heating  surface. 

3d.  Sufficient  liberating  surface  in  the  steam  drums  to 
insure  dry  steam,  with  large  body  of  water  in  reserve  to  draw 
from. 

4th.  A  steam  reservoir  or  steam  drum. 

5th.  Simplicity  in  construction  ;  accessibility  for  cleaning  and 
inspection. 

6th.  A  header,  which  in  its  design  provides  for  the  unequal 
expansion  and  contraction. 


HANDBOOK    ON    ENGINEERING. 


503 


Illustration  above  is  that  of  a  Horizontal  Safety  Water  Tube 
Boiler,  manufactured  by  the  John  O'Brien  Boiler  Works  Company, 
of  St.  Louis,  U.  S.  A. 

Down  draft  furnace*  —  A  great  many  of  these  boilers  are  fit- 
ted with  the  down  draft  furnaces,  and  the  above  illustration  shows 
the  style  of  same,  together  with  the  manner  in  which  they  are 
connected. 

A  full  and  complete  description  of  these  furnaces  is  given  on 
page  522. 

Description*  —  In    construction,  this    type  of    boiler   consists 


504  HANDBOOK    ON    ENGINEERING. 

simply  of  a  front  and  rear  water  leg  or  header,  made  approx- 
imately rectangular  in  shape,  overhead  combination  steam  and 
water  drum  or  drums  and  with  circulating  water  tubes,  as 
shown  in  cut,  which  extend  between  and  connect  both  front  and 
rear  headers,  being  thoroughly  expanded  into  the  tube  sheets. 
The  tubes  are  inclined  on  a  pitch  of  one  inch  to  the  foot  and  the 
rear  header  being  longer  than  the  front  one,  the  overhead  drum 
connecting  both  headers  lies  perfectly  level  when  the  boiler  is  set 
in  position.  The  connection  of  the  headers  with  the  combined 
steam  and  water  drum  is  made  in  such  a  manner  as  to  give  prac- 
tically the  same  area  as  the  total  area  of  the  tubes,  so  there  is  no 
contraction  of  area  in  the  course  of  circulation ;  and  extending 
between  and  connecting  the  inside  faces  of  the  water  legs, 
which  form  end  connections  between  these  tubes  and  the  com- 
bined steam  and  water  drums  or  shells,  placed  above  and  parallel 
with  them,  also  a  steam  drum  above  these,  assures  absolutely  dry 
steam  and  a  large  steam  space,  also  a  large  water  space.  The  water 
legs  are  made  larger  at  the  top,  about  11  inches  wide,  and  at  the 
bottom  about  7  inches  wide,  which  is  a  great  advantage,  allowing 
the  globules  of  steam  to  pass  quickly  up  the  water  legs  to  the 
steam  and  water  drums.  The  water,  as  it  sweeps  along  the 
drums,  frees  itself  of  steam  ;  then  it  goes  down  the  back  connec- 
tion until  it  meets  the  inclined  tubes,  meeting  on  its  passage  a 
gradually  increasing  temperature,  till  the  furnace  is  again  reached, 
where  the  steam  formed  on  the  way  is  directly  carried  up  in  the 
drum  as  before.  The  tubes  extend  between  and  connect  both  the 
front  and  rear  headers  and  are  thoroughly  expanded  into  the 
tube  sheets.  Opposite  the  end  of  each  tube  there  is  an  oval 
hand-hole  slightly  larger  than  the  tube  proper  through  which  it 
can  be  withdrawn.  It  will  be  noted  that  the  throat  of  each 
water  leg  is  11  times  the  total  tube  area.  The  rapid  and 
unimpeded  circulation  tends  to  keep  the  inside  surface  clean  and 
floats  the  scale-making  sediment  along  until  it  reaches  the  back 


HANDBOOK    ON    ENGINEERING. 


505 


water  leg,  where  it  is  carried  down  and  settles  in  the  bottom  of  leg, 
where  it  is  blown  off  at  regular  intervals. 


Steadiness  of  water  level.  — The  large  area  of  surface  at  water 
line  and  the   ample  passages  for   circulation,  secure  a  steadiness 


506  HANDBOOK    ON    ENGINEERING. 

of  water  level  unsurpassed  by  any  boiler.  This  is  a  most  im- 
portant point  in  boiler  construction  and  should  always  be  consid- 
ered when  comparing  boilers.  The  water  legs  are  stayed  by  hol- 
low stay-bolts  of  hydraulic  tubing  of  large  diameter,  so  placed  that 
two  stays  support  each  tube  and  hand-hole  and  are  subjected  to  only 
very  slight  strain.  Being  made  of  heavy  material,  they  form  the 
strongest  parts  of  the  boiler  and  its  natural  supports.  The  water 
legs  are  joined  to  the  shell  by  flanged  and  riveted  joints  and  the 
drum  is  cut  away  at  these  two  points  to  make  connection  with  in- 
side of  water  leg,  the  opening  thus  made  being  strengthened  by 
special  stays,  so  as  to  preserve  the  original  strength.  The  shells 
are  cylinders  with  heads  dished  to  form  part  of  a  true  sphere. 
The  sphere  is  everywhere  as  strong  as  the  circular  seam  of  the 
cylinder,  which  is  well  known  to  be  twice  as  strong  as  the  side 
seam ;  therefore,  the  heads  require  no  stays.  Both  the  cylinder 
and  the  spherical  heads  are,  therefore,  free  to  follow  their  natural 
lines  of  expansion  when  put  under  pressure. 

The  illustration  on  page  505  plainly  shows  the  formation  of 
the  front  water  leg  or  header  in  this  type  of  water  tube  boiler. 

It  will  be  seen  that  the  hand  plates  are  all  oval  in  shape,  allow- 
ing each  one  to  be  removed  from  its  respective  hole ;  also,  the 
manner  of  bracing  with  hollow  stay-bolts  is  shown. 

Note  that  the  feed  pipes  for  supplying  furnace  are  equipped 
with  oval  hand  plates  to  facilitate  cleaning. 

Walling  in,  —  In  setting  the  boiler,  its  front  water  leg  is  placed 
firmly  on  a  set  of  strong,  cast-iron  columns  bolted  and  braced  to- 
gether by  the  door  frames  and  dead-plates  and  forming  the  fire 
front.  This  is  the  fixed  end.  The  rear  water  legs  rest  on  rollers 
which  are  free  to  move  on  cast-iron  plates  firmly  set  in  the  ma- 
sonry of  the  low  and  solid  rear  wall.  Thus  the  boiler  and  its  walls 
are  each  free  to  move  separately  during  expansion  or  contraction, 
without  loosening  any  joints  in  the  masonry. 

On  the  lower,  and  between  the  upper  tubes,   are  placed  light 


HANDBOOK    ON    KN<;  IN  BERING.  507 

fire-brick  tiles.  The  lower  tier  extends  from  the  front  water  leg 
to  within  a  few  feet  of  the  rear  one,  leaving  there  an  upward  pass- 
age across  the  rear  ends  of  the  tubes  for  the  flame.  The  upper 
tier  closes  into  the  rear  water  leg  and  extends  forward  to  within 
a  few  feet  of  the  front  one,  thus  leaving  an  opening  for  the  gases 
in  front.  The  side  tiles  extend  from  side  walls  to  tile  bars  and 
close  up  to  the  front  water  leg  and  front  wall, 'and  leave  open  the 
final  uptake  for  the  waste  gases. 

The  gases  being'  thoroughly  mingled  in  their  passage  between 
the  staggered  tubes,  the  combustion  is  more  complete,  and  the 
gases  impinging  against  the  heating  surface  perpendicularly,  in- 
stead of  gliding  along  the  same  longitudinally,  the  absorption  of 
the  gas  is  more  thorough.  The  draft  area,  being  much 
larger  than  in  lire  tube  boilers,  gives  ample  time  for  the 
absorption  of  the  heat  of  the  gases  before  their  exit  to  the 
chimney. 

DESCRIPTION  OF  THE  HEINE  SAFETY  BOILER. 

The  boiler  is  composed  of  lap-welded  wrought-iron  tubes  ex- 
tending between  and  connecting  the  inside  faces  of  two  "  water 
legs,"  which  form  the  end  connections  between  these  tubes  and 
a  combined  stearn  and  water  drum  or  ' '  shell  ' '  placed  above  and 
parallel  with  them.  (Boilers  over  200  horse-power  have  two  such 
shells.)  These  end  chambers  are  of  approximately  rectangular 
shape,  drawn  in  at  top  to  fit  the  curvature  of  the  shells.  Each  te 
composed  of  a  head  plate  and  a  tube  sheet  FLANGED  ALL  AROUND 
AND  JOINED  AT  BOTTOM  and  sides  by  a  butt  strap  of  same  material, 
strongly  riveted  to  both.  The  water  legs  are  further  stayed  by 
hollow  stay-bolts  of  hydraulic  tubing  of  large  diameter,  so  placed 
that  two  stays  support  each  tube  and  hand-hole  and  are  subjected 
to  only  very  slight  strain.  Being  made  of  heavy  metal,  they  form 
the  strongest  parts  of  the  boiler  and  its  natural  supports.  The 


508 


HANDBOOK    ON    ENGINEERING. 


water  legs  are  joined  to  the  shell   by   flanged  and  riveted  joints, 
and  the  drum  is  cut  away  at  these  two  points  to  make  connection 


with  inside  of  water  leg,  the  opening  thus  made  being  strength- 
ened by  bridges  and  special  stays  so  as  to  preserve  the  original 
strength. 

48 


HANDBOOK    ON    ENGINEERING.  f>()9 

The  shells  ai'e  cylinders  with  heads  dished  to  form  parts  of  a 
true  sphere.  The  sphere  is  everywhere  as  strong  as  the  circle 
seam  of  the  cylinder,  which  is  well  known  to  be  twice  as  strong  as 
its  side  seam.  Therefore,  these  heads  require  no  stays.  Both 
the  cylinder  and  its  spherical  heads  are,  therefore,  free  to  follow 
their  natural  lines  of  expansion  when  put  under  pressure.  Where 
flat  heads  have  to  be  braced  to  the  sides  of  the  shell,  both  suffer 
local  distortions  where  the  feet  of  the  braces  are  riveted  to  them, 
making  the  calculations  of  their  strength  fallacious.  This  they 
avoid  entirely  by  their  dished  heads.  To  the  bottom  of  the  front 
head  a  flange  is  riveted,  into  which  the  feed-pipe  is  screwed. 
This  pipe  is  shown  in  the  cut  with  angle  valve  and  check  valve 
attached.  On  top  of  shell,  near  the  front  end,  is  riveted  a  steam 
nozzle  or  saddle,  to  which  is  bolted  a  tee.  This  tee  carries  the  steam 
valve  on  its  branch,  which  is  made  to  look  either  to  front,  rear, 
right  or  left ;  on  its  top  the  safety  valve  is  placed.  The  saddle 
has  an  area  equal  to  that  of  stop  valve  and  safety  valve  combined. 
The  rear-head  carries  a  blow-off  flange  of  about  same  size  as  the 
feed  flange,  and  a  manhead  curved  to  fit  the  head,  the  manhole 
supported  by  a  strengthening  ring  outside.  On  each  side  of  the 
shell  a  square  bar,  the  tile-bar,  rests  loosely  in  flat  hooks  riveted 
to  the  shell.  This  bar  supports  the  side  tiles,  whose  other  ends 
rest  on  the  side  walls,  thus  closing  the  furnace  or  flue  on  top. 
The  top  of  the  tile-bar  is  two  inches  below  low  water  line.  The 
bars  '  rise  from  front  to  rear  at  the  rate  of  one  inch  in  twelve. 
When  the  boiler  is  set,  they  must  be  exactly  level,  the  whole 
boiler  being  then  on  an  incline,  i.  e.,  with  a  fall  of  one  inch  in 
twelve  from  front  to  rear.  It  will  be  noted  that  this  makes  the 
height  of  the  steam  space  in  front  about  two-thirds  the  diam- 
eter of  the  shell,  while  at  the  rear  the  water  occupies  two-thirds 
of  the  shell,  the  whole  contents  of  the  drum  being  equally  divided 
between  steam  and  water.  The  importance  of  this  will  be  ex- 
plained hereafter. 


510 


HANDBOOK    ON    ENGINEERING. 


The  tubes  extend  through  the  tube  sheets,  into  which  llicv  .-in- 
expanded  with  roller  expanders ;  opposite  the  end  of  each  and  in 
the  head-plates,  is  placed  a  hand-hole  of  slightly  larger  diarn- 


eter  than  the  tube,  and  through  which  it  can  bo  withdrawn. 
These  hand-holes  are  closed  by  small  cast-iron  hand-hole  plates, 
which,  by  an  ingenious  device  for  locking,  can  be  removed  in,  a 


HANDBOOK    ON     KN<  J I  NKEKI  \(J .  511 

lew  seconds  to  inspect  or  clean  ;i  tube.  The  accompanying  cut 
shows  these  hand-hole  plates  marked  //.  In  the  upper  corner 
one  is  shown  in  detail,  If2  being  the  top  view,  7/3  the  side  view 
of  the  plate  itself,  the  shoulder  showing  the  place  for  the  gasket. 
//'l  is  the  yoke  or  crab  placed  outside  to  support  the  bolt  and  nut. 
Inside  of  the  shell  is  located  the  mud  drum  />,  placed  well 
below  the  water  line,  usually  parallel  to  and  3  inches  above  the 
bottom  of  the  shell.  It  is  thus  completely  immersed  in  the  hot- 
test water  in  the  boiler.  It  is  of  oval  section,  slightly  smaller 
than  the  manhole,  made  of  strong  sheet-iron  with  cast-iron  heads. 
It  is  entirely  inclosed  except  about  18  inches  of  its  upper 
portion  at  the  forward  end,  which  is  cut  away  nearly  parallel  to 
the  water  line.  Its  action  will  be  explained  below.  The  feed- 
pipe F  enters  it  through  a  loose  joint  in  front ;  the  blow-off  pipe 
N  is  screwed  tightly  into  its  rear-head,  and  passes  by  a  steam- 
tight  joint  through  the  rear-head  of  the  shell.  Just  under  the 
steam  nozzle  is  placed  a  dry  pan  or  dry  pipe  A.  A  deflection 
plate  L  extends  from  the  front  head  of  the  shell,  inclined  up- 
wards, to  some  distance  beyond  the  mouth  or  throat  of  the  front 
water  leg.  It  will  be  noted  that  the  throat  of  each  water  leg  is 
large  enough  to  be  the  practical  equivalent  of  the  total  tube  area, 
and  that  just  where  it  joins  the  shell  it  increases  gradually  in 
width  by  double  the  radius  of  the  flange. 

Erection  and  walling  in.  —  In  setting  the  boiler,  its  front 
water  leg  is  placed  firmly  on  a  set  of  strong  cast-iron  columns, 
bolted  and  braced  together  by  the  door  frames,  deadplate,  etc., 
and  forming  the  fire  front.  This  is  the  fixed  end.  The  rear 
water  leg  rests  on  rollers,  which  are  free  to  move  on  cast-iron 
plates  firmly  set  in  the  masonry  of  the  low  and  solid  rear  wall. 
Wherever  the  brickwork  closes  in  to  the  boiler,  broad  joints  are 
left  which  are  filled  in  with  tow  or  waste  saturated  with  fireclay, 
or  other  refractory  but  pliable  material.  Thus  the  boiler  and  its 
walls  are  each  free  to  move  separately  during  expansion  or  con- 


HANDBOOK    ON    ENGINEERING. 

traction  without  loosening  any  joints  in  the  masonry.  On  the 
lower,  and  between  the  upper  tubes,  arc  placed  light  fire-brick 
tiles.  The  lower  tier  extends  from  the  front  water  leg  to  within 
a  few  feet  of  the  rear  one,  leaving  there  an  upward  passage  across 
the  rear  ends  of  the  tubes  for  the  flame,  etc.  The  upper  tier 
closes  in  to  the  rear  water  leg  and  extends  forward  to  within  a 
few  feet  of  the  front  one,  thus  leaving  the  opening  for  the  gases  in 
front.  The  side  tiles  extend  from  side  walls  to  tile  bars  and  close 
up  to  the  front  water  leg  and  front  wall,  and  leave  open  the  final 
uptake  for  the  waste  gases  over  the  back  part  of  the  shell,  which 
is  here  covered  above  water  line  with  a  rowlock  of  firebrick  rest- 
ing on  the  tile  bars.  The  rear  wall  of  the  setting  and  one  paral- 
lel to  it  arched  over  the  shell  a  few  feet  forward,  form  the  uptakes. 
On  these  and  the  rear  portion  of  the  side  walls  is  placed  a  light 
sheet-iron  hood,  from  which  the  breeching  leads  to  the  chimney. 
When  an  iron  stack  is  used,  this  hood  is  stiffened  by  L  and  T 
irons  so  that  it  becomes  a  truss  carrying  the  weight  of  such  stack 
and  distributing  it  to  the  side  walls. 

Longitudinal  section  of  Heine  Boiler  and  its  operation*  — 
The  boiler  being  filled  to  middle  water  line,  the  fire  is  started  on 
the  grate.  The  flame  and  gases  pass  over  the  bridge  wall  and 
under  the  lower  tier  of  tiling,  finding  in  the  ample  combustion 
chamber  space,  temperature  and  air  supply  for  complete  combus- 
tion, before  bringing  the  heat  in  contact  with  the  main  body  of  the 
tubes.  Then,  when  at  its  best,  it  rises  through  the  spaces  be- 
tween the  rear  ends  of  the  tubes,  between  rear  water  leg  and  back 
end  of  the  tiling,  and  is  allowed  to  expand  itself  on  the  entire 
tube  heading  surface  without  meeting  any  obstruction.  Ample 
space  makes  leisurely  progress  for  the  flames,  which  meet  in  turn 
all  the  tubes,  lap  round  them,  and  finally  reach  the  second  uptake 
at  the  forward  end  of  the  top  tier  of  tiling,  with  their  temperature 
reduced  to  less  than  900°  ^Fahrenheit.  This  has  been  measured 
here,  while  wrought  iron  would  melt  just  above  the  lower  tubes  at 


II AM) MOOR    ON    ENGINEERING. 


r>i3 


rear  end,  showing  a  reduction  of  temperature  of  over  1,800°  Fahr. 
between  the  two  points.  As  the  space  is  studded  with  water 
tubes,  swept  clean  by  a  positive  and  rapid  circulation,  the  absorp- 
tion of  this  great  amount  of  heat  is  explained.  The  gases  next 
travel  under  the  bottom  and  sides  of  shell  and  reach  the  uptake 
at  just  the  proper  temperature  to  produce  the  draft  required. 
This  varies,  of  course,  according  to  chimney,  fuel  required,  etc. 
With  boilers  running  at  their  rated  capacity,  450°  Fahrenheit  are 


A  furnace  that  is  used  in  the  East  a  great  deal. 


seldom  exceeded.  Meanwhile,  as  soon  as  the  heat  strikes  the 
tubes,  the  circulation  of  the  water  begins.  The  water  nearest  the 
surface  of  the  tubes  becoming  warmer,  rises,  and  as  the  tubes  are 
higher  in  front,  this  water  flows  towards  the  front  water  leg 
where  it  rises  into  the  shell,  while  colder  water  from  the  shell 
falls  down  the  rear  water  leg  to  replace  that  flowing  forward  and 
upward  through  the  tubes.  This  circulation,  at  first  slow,  in- 

33 


514  HANDBOOK    ON    ENGINEERING. 

creases  in  speed  as  soon  as  steam  begins  to  form.  Then  the 
speed  with  which  the  mingled  current  of  steam  and  water  rises  in 
the  forward  water  leg  will  depend  on  the  difference  in  weight  of 
this  mixture,  and  the  solid  and  slightly  colder  water  falling  down 
the  rear  water  leg.  The  cause  of  its  motion  is  exactly  the  same 
as  that  which  produces'draft  in  a  chimney. 


Plain  Vertical  Tubular  Boiler- 


This  cut  shows  the  place  for  gauge  cocks  and  water  glass  in  an 
upright  boiler. 


HANDBOOK    ON    ENGINEERING. 


515 


060OCHDOOOO 

ooooo,  ooooo 
ooooo  ooooo 
ooooo  ooooo 
oooo  oooo 

O    ^ft-rfk    O 


The  above  cut  shows  the  water-column  iu  its  proper  place. 


HANDBOOK    ON    ENGINEERING. 


juao  aod  OS 


•OinSSOJJ 


fsl 


60,000  ten 
strengt 
1-6,  10,00 


}U9O  JOd 


^uoo  J9d  OS 


-*S88&SS8S88SS383»2S5BS 


e«  _  oo  t- 1^  Li  mo; 'at  gTojj  £;  2;  :;  r£ 


38! 


»—  icooocoi^-'-H-^c^       co^o-««''^ioi^*oO'—  ^co-^'OO'—  tjccor—  -rf/Dci 

-*  -5«  -52  o  »  »  <S>O»  !•-  •-<  3  M  eo  «  rio  ooB  t»2S  •*  35  o  01  r-S5  r-. 


i  «  <M  e-«  i— 1 1— i  i-i  • 


_•«? 


,000  ten 
strengt 
-6,  9,166 


juao  ja 


1 


tens 
ngth 
7,500. 


jo 


juao  aad 


I1 


HANDBOOK    ON    ENGINEERING. 


517 


SS 


oo  QO  i       o  n  s     n  w  i   ot  o  A  o  «H 


518 


HANDBOOK    ON    ENGINEERING. 


2  £2- 

s 


B 

§21 

Ps 


gth, 


f! 


owable  on  Boilers 
Gover 


0,000  ten 
stren 
1-6,  10 


55,000  tensile 
strength, 
1-6,  9,166,6. 


1H90  J9d 


ad  02 


•JU80  jad 


,000  tensil 
strength, 
1-6,  8,333.3. 


*  HrC 


5SS8SS5S 


cOiroorr''«*<o«DO5o>occD-«J<e>aeco;e-»ocD^Hr—  -^<  t- 
5  S     «  Ss  »fi  f-F-ao  35  o  o  H  o  2  55  »  t^ooooos  »  o  ^ 


t~  CO  QO  CO  c£>  SO 


r~-  CD  I  —         OS  ^  O5  * 

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HANDBOOK    ON    ENGINEERING. 


519 


to  £):o  £•»:$£      co  o  »M  — <  •*  10  •<*      m -M      -*      i-ccoox>»— (iot--f-*coi~co^sio--ootOi— i      IO--KH 

HOt£><Mr-.C3QOai-*JOaOr-«X:|--r-i»         l-OO5O-*lT.  MS-JX^rHlOL^^^eOt-WCr^OiOrHT^r-lt^OSr-t 


HANDBOOK  ON  ENGINEERING. 


ooooo  ooooo 


'OO 
OOOOO  OOOOO 

oooo  oooo 
o  An^  o 


—  —  e'-e% 

The  above  cut  shows  the  proper  place  for  closing  in  the  boiler 
on  the  side  —  also  the  space  between  side  of  boiler 
and  side  walls. 


HANDBOOK    ON    ENGINEERING, 


521 


The  above  cut  shows  the  proper  place  for  gauge-cocks  in  a 
submerged  tube  boiler. 


522 


HANDBOOK    ON    ENGINEERING. 


THE  AMOUNT  OF    MATERIAL   REQUIRED  TO  BRICK 
UP  BOILERS  OF  DIFFERENT  SIZE. 


~  • 

|« 

o 

y  >j  ^o 

£2^1* 

<o  ~ 

2  o 

P 

s 

«^2^ 

I 

II 

is 

|  !  g>«  §  f 

X  W 

1 

« 

sfi^'i 

cc  b 

tc>^ 

O   o   5  rt 

72"x22' 

18" 

10,500 

2,500 

18  bu. 

88 

8 

9  bbl. 

72"x20' 

18" 

10,000 

2,300 

18  bu. 

80 

8 

8  bbl. 

72"xl8' 

18" 

9,500 

2,200 

17  bu. 

72 

7 

8  bbl. 

60"x20' 

18" 

9,500 

2,200 

17  bu. 

80 

7 

8  bbl. 

60"xl8' 

18" 

9,000 

2,000 

16  bu. 

72 

7 

8  bbl. 

54"x20' 

18" 

8,700 

,900 

15  bu. 

80 

6 

8  bbl. 

54"xl8' 

18" 

8,000 

,800 

15  bu. 

72 

6 

8  bbl. 

54"xl6' 

18" 

7,500 

,700 

14  bu. 

64 

6 

7  bbl. 

48"xl8' 

18" 

7,500 

,600 

14  bu. 

72 

6 

7  bbl. 

48"xl6' 

18" 

7,200 

,500 

14  bu. 

64 

5 

7  bbl. 

42"xl8' 

18" 

7,000 

,400 

12  bu. 

72 

5 

7  bbl. 

42"xl6' 

18" 

6,500 

,300 

12  bu. 

64 

4 

7  bbl. 

If  13"  wall  i  less  on  Red  Brick. 

THE  DOWN  DRAUGHT  FURNACE. 

The  down  draught  furnace  is  noted  for  being  one  of  the  best 
smoke  preventing  furnaces  in  the  market,  while  at  the  same  time 
the  cheapest  kind  of  coal  can  be  used. 

The  down  draught  furnace  made  a  good  smoke  record,  even 
with  overworked  boilers,  doing  variable  work,  and  with  a  marked 
economy  in  fuel.  My  experience  with  the  down  draught  furnace, 
I  feel  safe  in  saying  that  smoke  from  boiler  furnaces  can  now  be 
abated  by  practical  means,  without  hardship,  no  matter  what  the 
type  of  boiler. 

Directions  for  firing  the  Down  Draught  Furnace*— When 
firing  the  furnace,  throw  the  coal  evenly  over  the  entire  grate 
surface,  from  6  to  8  inches  in  depth,  a  little  heaviest  at  the 
rear  end  of  the  furnace.  Do  not  put  in  too  much  coal  — 
burn  more  air ;  and  economize  with  your  fuel  and 


HANDBOOK    ON    ENGINEERING. 


523 


do  not  pile  up  the  coal  in  front  near  the  door.  Never  fire  any 
fresh  coal  on  the  lower  grates  ;  let  in  air  below  the  lower  grates. 
When  poking  the  fire,  run  the  slice-bar  down  between  the  water 
grates  and  back  the  full  length  of  the  grates  ;  then  raise  the  slice- 
bar  and  gently  shake  the  coal,  and  then  pull  it  out  without  stir- 
ring up  the  fire.  Never  turn  the  fire  over  so  that  black  coal  gets 
down  upon  the  water  grates,  unless  there  is  a  large  clinker  to  re- 
move. Never  give  the  top  grates  a  general  cleaning,  so  as  to 
leave  a  portion  of  the  grates  uncovered  and  the  remainder  with  a 
hot  fire  on  them,  as  this  causes  an  uneven  expansion  in  the  differ- 
ent tubes  forming  the  water  grates,  and  is  liable  either  to  bend 
the  tubes  or  strip  off  the  threads  where  they  enter  the  drums. 
When  the  top  fire  becomes  clogged  with  clinkers  so  that  you  can- 


Down  Draught  Furnace. 

not  keep  up  steam,  run  in  the  slice-bar  and  raise  the  clinkers  to 
the  top  of  the  fire  ;  remove  the  large  clinkers,  leave  the  small  ones 
alone,  and  put  on  afresh  fire.  The  lower  grates  must  have  proper 


524 


HANDBOOK    ON    ENGINEERING. 


attention.  The  coals  must  be  raked  over  evenly  and  all  holes 
filled  up,  particular  care  being  taken  that  the  grates  are  perfectly 
covered  all  over.  If  considerable  coals  have  accumulated  on  the 


.  ja"*L i~r J.  iv-4 


View  of  the  Down  Draught  Furnace. 

lower  grates  and  the  air  spaces  are  closed  with  ashes  or  clinkers, 
the  slice-bar  must  be  used  and  the  clinkers  raised  up  and  turned 
over  and  the  larger  ones  removed.  It  is  best  to  remove  the  clink- 
ers every  two  or  three  hours,  leaving  the  coals  to  burn  up. 


SPECIFICATIONS  FOR  ONE    SIXTY-INCH     HORIZONTAL     SIX= 
INCH   FLUE   BOILER. 

General  directions*  — •  There  will  be  one  boiler  20  feet  long  from 
out  to  out  of  heads  and  60  inches  inside  diameter. 

Material,  quality,  thickness,  etc*  —  Material  in  shell  of  the 
above  named  boiler  to  be  made  of  homogeneous  flange  steel  T5^" 
thick,  having  a  tensile  strength  of  not  less  than  60,000  Ibs.  to 


HANDBOOK    ON    ENGINEERING. 


525 


526  HANDBOOK    ON    ENGINEERING. 

the  square  inch  of  section,  with  not  less  than  56  per  cent  ductil- 
ity, as  indicated  by  contraction  of  area  at  point  of  fracture  under 
test,  or  by  an  elongation  of  25  per  cent  in  length  of  8  inches. 
Heads  must  be  J"  thick  and  of  the  same  quality  of  steel  as  that 
in  the  shell.  All  plates  and  heads  must  be  plainly  stamped  with 
the  maker's  name,  and  tensile  strength. 

Tubes,  size,  number  and  arrangement*  —  The  boiler  must 
contain  18-6"  lap-welded  flues,  riveted  to  the  heads  with  Ten  £" 
rivets  in  each  head  ;  said  flues  must  be  made  of  charcoal  iron  of  the 
best  American  make,  standard  thickness,  equal  to  the  National 
Tube  Works  Company's  make.  All  flues  must  have  at  least  3 
inch  clear  space  between  them,  and  not  less  than  3  inches 
between  flues  and  shell.  All  flanging  of  heads  must  be  free  from 
flaws  or  cracks  of  any  description,  and  properly  annealed  in  an 
annealing  oven  before  riveting  to  the  boiler.  If  4-inch  flues  are 
wanted  in  place  of  6 -inch,  the  boiler  must  have  44  best  lap- 
welded  tubes,  4"  in  diameter  and  20  feet  long,  set  in  vertical  and 
horizontal  rows,  with  a  clear  space  between  them,  vertically  and 
horizontally  of  11",  except  the  central  vertical  space,  which  is  to 
be  4  inches.  Holes  for  tubes  to  be  neatly  chamfered  off  on  the 
outside.  Tubes  to  be  set  with  a  Dudgeon  expander,  and  beaded 
down  at  each  end. 

Riveting*  —  The  longitudinal  seams  of  the  boiler  must  be 
above  the  fire  line,  and  have  a  TRIPLE  row  of  rivets  ;  all  rivets  to 
be  J"  in  diameter ;  and  all  rivets  to  be  of  sufficient  length  to 
form  upheads  equal  in  size  to  the  pressed  heads  of  same.  The 
rivets  in  the  longitudinal  seams  must  be  spaced  31"  apart 
from  center  to  center,  anc[  the  rows  of  same  to  be  pitched  2T3^" 
apart  from  center  to  center,  so  as  to  give  an  efficiency  of  the 
joint  of  T7¥6Q  per  cent  of  the  solid  plate.  Transverse  seams  to 
be  single  riveted  with  same  size  rivets  as  those  in  the  longitudinal 
seams  pitched  2"  apart  from  center  to  center.  Care  must  be 
taken  in  punching  and  drilling  holes  that  they  may  come  fair  in 


HANDBOOK    ON    ENGINEERING.  527 

construction;  the  use  of  adrift-pin  to  bring  blind,  or  partially 
blind  holes  in  line  will  be  sufficient  cause  for  the  rejection  of 
the  boiler. 

Calking*  —  The  edges  of  the  plates  to  be  planed  and  beveled 
before  making  up  the  boilers,  and  the  calking  to  be  done  with 
round  nose  tools,  pneumatically  driven  ;  no  split  or  wedge  calk- 
ing will  be  allowed. 

Bracing. —  There  must  be  22  braces  in  the  boiler,  one  inch  area 
at  least,  be  nine  above  the  flues  on  the  front  head  and  nine  similar 
ones  on  the  back  head,  none  of  which  shall  be  less  than  3'  6"  long, 
made  of  good  refined  iron  and  securely  riveted  to  the  heads ;  the 
other  end  to  be  extended  to  the  shell  of  boiler  and  riveted  thereto 
with  two  J''  rivets.  Care  must  be  exercised  in  the  setting  of 
them,  so  they  may  bear  uniform  tension.  There  must  be  two 
braces  below  flues,  one  on  each  side  of  manhead,  and  riveted  to 
the  heads  with  two  J"  rivets.  The  back  end  of  brace  to  be  ex- 
tended backward  to  side  of  shell  and  riveted  thereto  by  means 
of  two  J"  rivets ;  and  two  braces  in  back  end  above  flues,  one 
on  each  side  and  riveted  the  same  as  the  other  two  below 
flues. 

Manholes*  —  The  boiler  to  have  two  manholes  of  the  Hercules 
or  Eclipse  pattern,  same  to  be  of  size  10"  x  15",  one  located  in 
front  head,  beneath  the  flues,  and  the  other  in  rear  head  above 
the  flues,  and  each  to  be  provided  with  a  lead  gasket,  grooved  lid, 
two  yokes  and  two  bolts.  The  proportion  of  the  whole  to  be 
such  as  will  leave"  it  as  strong  as  any  other  portion  of  the  head  of 
like  area. 

Steam  drum*  —  The  boiler  must  be  provided  with  one  steam 
drum  30"  in  diameter  by  5'  in  length r  shell  plates  of  which  are  to 
be  Ty  thick  and  heads  |"  thick,  of  the  same  quality  of  material 
as  that  in  the  boiler.  The  heads  must  be  bumped  to  a  radius  so 
as  to  give  as  near  as  practicable  equal  strength  as  to  that  in  the 
shell  without  bracing.  The  longitudinal  seams  of  the  drum  are 


528  HANDBOOK    ON    ENGINEERING. 

to  be  doubly  riveted  with  ^"  diameter  rivets,  pitched  2^"  jipnrt 
from  center  to  center,  so  as  to  give  an  efficiency  of  the  joint  of 
TO\  Per  cen^  °^  the  solid  plate. 

Manhole  in  drum. — The  drum  must  be  provided  with  Her- 
cules or  Eclipse  Patented  Manhole,  same  to  be  of  size  10"  x  15", 
located  in  the  center  of  one  head,  and  to  be  provided  with  a 
grooved  lid,  lead  gasket,  two  yokes  and  two  bolts.  The  propor- 
tion of  the  whole  to  be  such  as  will  leave  it  as  strong  as  any  other 
portion  of  the  head  of  like  area. 

To  attach  to  boilers.  —  The  steam  drum  must  be  attached  to 
the  boiler  by  means  of  two  flange  steel  connecting  legs,  8"  in 
diameter  by  12"  in  length,  and  securely  riveted  to  boiler  and 
steam  drum  shell. 

Mud  drum.  —  Boiler  must  be  provided  with  one  mud  drum 
24"  in  diameter  and  of  sufficient  length  so  that  each  end  may 
come  flush  with  the  outside  of  the  boiler  walls  on  each  side  ;  the 
quality  and  thickness  of  steel  to  be  the  same  as  that  specified  for 
the  steam  drum,  and  all  seams  to  be  single  riveted  ;  said  mud 
drum  to  be  provided  with  one  Hercules  or  Eclipse  Patent  Manhole 
in  one  end,  and  to  be  of  size  9"  x  14",  supplied  with  a  grooved 
lid,  lead  gasket,  two  yokes  and  two  bolts. 

To  attach  to  boiler.  —  The  mud  drum  is  to  be  attached  to 
boiler  by  means  of  8"  diameter  steel  connecting  leg,  about  16"  in 
length,  properly  riveted  to  boiler  and  mud  drum  shells. 

Flanges. —  The  boiler  to  have  one  8"  wrought  steel  flange  riv- 
eted on  top  of  steam  drum  ;  one  wrought  steel  flange  4"  in  diam- 
eter, about  5  feet  from  front  end  of  boiler  for  safety  valve  one 
2"  wrought  steel  flange  on  after  end  of  boiler  over  the  center  of 
mud  leg  for  supply  pipe  — -  all  flanges  to  be  threaded  ;  2"  hole  in 
mud  drum  for  blow-off  ;  also  2  1 J"  holes,  one  on  top  of  boiler 
and  one  on  end  near  bottom  of  boiler  for  water  column. 

Fusible  plugs.  —  To  have  two  fusible  plugs ;  one  inserted  in 
shell  from  inside  on  second  sheet,  or  about  5'  from  forwardend,  1 


HANDBOOK    ON    ENGINEERING. 

inch  above  flues  ;  one  plug  inserted  in  top  of  flue,  not  more  than 
three  !;eet  from  after  end. 

Trimmings*  —  Furnish  one  4"  spring  or  dead  weight  safety 
valve,  4"  diameter ;  one  water  combination  column  ;  provide  same 
with  two  1J"  valves  for  the  steam  and  water  connections  between 
the  boiler  and  column,  and  one  1"  valve  for  blow-pipe  ;  said  blow- 
pipe to  be  connected  with  ashpit ;  said  combination  barrel  to  be 
4''  diameter,  18''  long,  and  made  of  cast-iron.  Also,  furnish  one 
water  gauge  having  a  J"  x  15"  Scotch  glass  tube,  bodies  polished 
with  wood  wheels  and  guards,  rods,  bodies  threaded  £"  ;  three 
gauge  cocks  £"  register  pattern,  polished  brass  bodies  ;  one  steam 
gauge  with  10"  dial ;  one  2"  brass  feed  valve  with  2"  check 
valve ;  one  2"  globe  valve  for  blow-off  from  m.ud  drum ;  also  one 
asbestos  packed  stop-cock  for  same,  so  as  to  insure  against  the 
possibilities  of  a  leak  through  the  blow-pipe.  Water  column  to 
have  crosses  in  place  of  ells.  Crosses  to  have  brass  plugs. 

Castings,  grates,  doors,  etc*  —  The  boiler  must  be  provided 
with  a  heavy  three-quarter  fire  front  of  neat  design,  having  double 
tiring  and  ashpit  doors,  anchor  bolts  for  anchoring  fire  fronts  in 
place,  heavy  deadplates,  a  full  set  of  lire  liners  0"  deep  for  sup- 
porting firebrick  on  end,  front  and  rear  bearing  bars  ;  a  full  set 
of  ordinary  grate  bars  4  ft.  long,  soot  door  and  frame  for  cleaning 
out  rear  ashpit ;  a  full  set  of  skeleton  arch  plates  ;  12  heavy  buck 
staves  9  i'  long,  provided  with  tie  rods,  nuts  and  washers,  heavy 
back  stand  with  plate  and  expansion  roJlers  ;  also  furnish  wrought 
plates  to  cover  mud  drum. 

Fire  tools*  —  Furnish  in  addition  to  above  two  sets  of  fire  tools 
consisting  of  two  pokers,  two  hoes,  two  slice-bars,  two  claws,  and 
one  six  inch  flue  brush  with  j."  pipe  for  handle. 

Breeching* — Boiler  must  have  a  breeching  fitted  to  front  head 
and  fastened  thereto  by  means  of  bolts,  stays  and  suitable  pieces 
of  angle  iron,  bent  to  conform  to  circle  of  boiler.  The  underside 
of  breeching  is  to  run  across  the  head  between  the  lower  flues  and 

34 


530  HANDBOOK    ON    ENGINEERING. 

the  manhole,  leaving  the  manhole  freely  exposed ;  the  siaes  of 
breeching  are  to  be  made  of  T3¥"  steel,  the  front  and  dooi>  of  J" 
steel ;  said  doors  to  be  hung  by  means  of  strap  hinges,  rrovided 
with  suitable  fastenings  so  as  to  give  free  access  to  all  flues  when 
open. 

Uptake  and  damper*  —  An  uptake  having  an  area  of  1221 
square  inches  must  be  fitted  to  top  of  breeching.  vSaid  uptake 
must  be  of  convenient  form  for  attaching  to  a  stack  40"  in  diam- 
eter and  provided  with  a  close-fitting  damper  having  a  steel  hand 
attachment,  so  that  same  may  be  operated  convenient!}'  from  the 
boiler  room  floor. 

Smoke  stack.  —  There  is  to  be  provided  for  the  above  boiler 
one  smoke  stack  40"  in  diameter  by  90  feet  in  height,  half  of 
which  is  to  be  made  of  No.  8,  and  the  other  half  of  No.  10  best 
black  sheet  steel  throughout,  and  supplied  with  two  sets  of  four 
guy  rods,  each  consisting  of  f"  galvanized  wire  cable  guy  strand 
with  turn  buckles  for  same. 

In  general*  —  The  above-mentioned  boiler  must  be  made  of 
strictly  first-class  material  and  workmanship  throughout,  and  sub- 
jected to  a  hydrostatic  pressure  of  150  pounds  to  the  square  inch 
before  leaving  the  works  of  the  manufacture. 

Painting  boiler  breeching*  —  Smoke  stack  and  boiler  front, 
steam  and  mud  drum,  and  all  trimmings,  to  have  two  good  coats 
of  coal  tar. 

Masonry*  —  Boiler  to  be  set  in  good  substantial  masonry,  of 
hard  burned  brick  and  good  mortar,  made  of  clean,  sharp  sand 
and  fresh  burned  lime.  Walls  to  be  18"  thick.  The  outside  walls 
to  be  laid  up  of  selected  hard  burned  brick,  with  close  joints 
struck  smooth  and  rubbed  down.  The  sides,  end  and  bridge 
walls,  and  boiler  front,  to  have  a  foundation  of  24"  wide  and  12' 
deep,  laid  in  Portland  cement.  The  ash  pit  to  be  paved  with 
hard  burned  brick  set  on  edge  firmly,  imbedded  in  Portland 
cement.  For  a  distance  of  seven  feet  in  front  of  the  boiler  and 


HANDBOOK    ON    ENGINEERING.  531 

continuing  across  entire  width  of  front  of  boiler  setting  to  be 
paved  with  hard  burned  brick  set  on  edge,  firmly  imbedded  in 
sand.  The  walls  to  be  carried  up  to  the  full  height  and  a  row- 
lock course  of  brick  4"  thick  to  be  carried  over  top  of  boiler  from 
side  wall  to  side  wall,  extending  the  whole  length  of  boiler,  and 
the  entire  arch  to  be  plastered  over  on  the  outside  with  mortar. 
The  bridge  walls  to  be  24",  carried  up  to  within  6"  of  under 
side  of  boiler.  The  top  of  bridge  wall  to  be  of  fire  brick  and 
made  in  the  form  of  an  inverted  arch,  conforming  to  the  shell  of 
the  boiler.  The  space  under  boiler  and  back  of  bridge  wall  to 
the  back  end  of  boiler,  to  be  filled  in  with  earth  or  sand  and  the 
top  paved  with  brick,  and  taper  ing  from  bridge  wall  back  to  back 
end  to  12"  at  back  end,  and  in  a  similar  form  and  shape,  that  is, 
inverted  arch.  The  uptake  for  returning  the  smoke  and  heat  at 
back  end  of  boiler,  to  be  arched  over  from  rear  wall  against  the 
back  head  of  boiler  2"  above  the  tubes,  the  arch  being  made  of  arch 
fire  brick,  and  backed  up  with  red  brick.  Furnace  to  be  lined 
throughout  with  first  quality  fire  brick,  dipped  in  fire  clay  with 
close  joints  and  fire  brick  rubbed  to  place,  from  a  point  2"  below 
grates,  to  where  it  safes  in  against  boiler,  and  to  be  continued  fire 
brick  as  far  back  as  the  rear  end  of  setting  and  across  rear  end  of 
same ;  it  being  the  intent  that  all  interior  surfaces  of  the  setting 
with  which  the  heat  comes  in  contact,  shall  be  faced  with  fire 
brick.  Every  sixth  course  to  be  a  header  course. 

Smoke  connections*  —  The  connection  from  boiler  to  chimney 
to  be  made  of  No.  12  black  iron,  with  cleaning  door  and  damper 
in  same. 

BANKING  FIRES. 

Different  engineers  pursue  different  methods  in  banking  fires. 
One  method  is  to  push  the  fire  back  one-third  towards  the  bridge 
wall,  and  clean  off  the  grate  in  front.  Then  shovel  in  from  150 
to  300  Ibs.  of  fine  coal  on  top  of  the  fire,  closing  ash-pit  doors 


532  HANDBOOK    ON    ENGINEERING. 

and  leaving  furnace  doors  open,  with  damper  open  enough  to  let 
the  gases  escape.  Others  bank  after  this  fashion  but  close  all 
doors  and  air  holes,  leaving  the  damper  partially  open.  Another 
method  is  to  level  the  fire  all  over  the  grate,  and  shovel  in  from 
150  to  500  Ibs.  of  fine  coal,  —  depending  on  the  size  of  the 
grate, — and  then  cover  the  whole  surface  with  wet  ashes  to  a 
good  depth,  so  that  no  fire  nor  flame  can  be  seen,  then  close  the 
ash-pit  doors,  leaving  the  furnace  doors  ajar,  and  leave  the 
damper  partially  open  so  that  the  gases  may  escape.  In  the 
morning,  rake  out  the  ashes,  clean  the  fire,  and  throw  in  fresh 
coal. 

INSTRUCTIONS  FOR  BOILER  ATTENDANTS. 

The  following  instructions  apply  more  particularly  to  horizontal 
return  tubular  boilers,  although  in  a  general  way  they  are  appli- 
cable to  all  types  of  boilers. 

Never  start  a  fire  under  a  boiler  until  you  are  positively  certain 
that  there  is  sufficient  water  in  the  boiler,  — at  least  two  gauges 
of  water.  Do  not  trust  to  the  water  gauge  alone,  but  try  the 
gauge  cocks  also,  and  try  them  at  intervals  during  the  day,  be- 
cause the  water-gauge  pipe  connections  may  be  choked  and  cause 
a  false  water  level. 

Before  starting  a  fire  be  sure  that  the  blow-off  cock  is  closed 
and  not  leaking. 

Before  it  is  time  to  start  the  engine,  pump  up  three  gauges  of 
water,  and  blow  off  one  gauge,  in  order  to  get  rid  of  mud  and 
other  sediment.  If  the  boiler  has  a  surface  blow-off,  —  commonly 
called  a  ;;  skimmer,"  —  blow  off  the  scum  before  stopping  the 
engine  for  the  day. 

When  the  day's  work  is  done,  leave  three  gauges  of  water  in 
the  boiler,  to  allow  for  leakage  and  evaporation  during  the  night. 

Never  raise  steam  hurriedly.  Sudden  changes  of  temperature 
may  produce  fractures,  or  start  leaks. 


HANDBOOK    ON    ENGINEERING.  533 

In  starting  a  iire  in  a  furnace,  a  good  plan  is  to  cover  the  grate 
with  a  thin  layer  of  coal  and  to  place  the  shavings  and  wood  on 
the  coal  and  then  light  the  shavings. 

The  advantage  of  placing  a  covering  of  coal  on  the  grate  before 
the  wood  and  shavings,  is  that  it  is  a  saving  of  fuel,  as  the  heat 
that  would  be  transmitted  to  the  bars  is  absorbed  by  the  coal,  and 
the  bars  are  also  protected  from  the  extreme  heat  of  the  fresh 
lire. 

Lift  the  safety-valve,  — if  of  the  lever  pattern,  —  every  morn- 
ing while  raising  steam,  and  satisfy  yourself  that  it  is  in  good 
working  order,  and  that  the  pi  is  set  at  the  proper  point  on  the 
lever.  The  most  disastrous  explosions  have  occurred  with  boilers 
whose  safety-valves  had  been  stuck  down  or  overloaded. 

Keep  the  boiler  shell  free  of  soot.  Soot  is  a  very  good  non- 
conductor of  heat,  and  considered  worse  than  scale  inside  of  a 
boiler. 

Keep  your  boiler  tubes  free  from  soot  and  dust.  Choked  tubea 
impair  the  draft.'  The  tubes  should  be  cleaned  twice  a  week,  or 
oftener. 

Soot  collects  also  in  a  stack  or  chimney  and  in  the  connection 
between  the"  breeching  "and  stack,  and  interferes  with  the  draft. 

Open  your  boiler  every  two  weeks,  or,  as  often  as  necessary, — 
depending  on  the  kind  of  feed-water  used, — and  clean  out  the 
mud  and  scale.  At  the  same  time  examine  all  of  the  stays,  and 
see  that  they  are  taut  and  in  good  order.  Also,  look  for  pitting 
around  the  mud-drum  connection,  and  for  grooving  in  the  side 
seams.  Examine  all  outlets  and  pipe  connections,  and  look  for 
indications  of  "  bagging  "  in  the  furnace  sheets. 

Clean  off  the  fusible  plugs  both  inside  and  outside  of  the  boiler. 
A  fusible  plug  covered  with  soot  on  the  fire  side,  and  with  scale 
on  the  water  side,  is  no  longer  a  "  safety  plug."  Renew  the 
filling  in  safety  plugs,  at  least  once  a  year.  They  are  filled  with 
pure  Banca  tin. 


534  HANDBOOK    ON    ENGINEERING. 

Be  perfectly  satisfied  that  your  boiler  is  in  good  condition 
internally  before  you  close  it  up. 

Just  as  soon  as  you  have  fastened  the  man-head  in  its  place, 
turn  on  the  feed-water  until  you  get  at  least  three  gauges  of  water. 
Fires  have  been  built  under  empt}^  boilers,  and  will  be  again,  if 
you  forget  to  turn  on  the  feed  water  after  cleaning  out. 

Do  not  empty  a  boiler  while  it  is  under  steam  pressure,  but 
allow  it  to  get  cold  before  letting  the  water  run  out. 

If  you  are  in  a  great  hurry  and  can't  wait  for  the  boiler  to  cool 
down,  nor  for  the-  brickwork  or  anything  else  to  cool  down,  draw 
the  fire  and  open  the  furnace  and  ash-pit  doors,  then  turn  on  the 
feed  water,  and  from  time  to  time  blow  out,  until  the  steam  gauge 
shows  no  pressure  ;  then  shut  .off  the  feed-water,  raise  the  safety 
valve,  open  the  blow-off  cock,  then  open  up  the  boiler. 

Before  opening  a  man -hole,  lift  the  safety-valve,  so  as  to  be 
sure  that  there  is  neither  pressure  nor  vacuum  in  the  boiler. 

Look  well  after  the  brick-work  surrounding  your  boiler,  and 
stop  all  cracks  in  tne  walls  with  mortar  or  cement,  as  soon  as 
discovered.  They  impede  the  draft,  and  cool  the  plates  of  the 
boiler,  causing  a  waste  of  fuel. 

See  that  the  bridge- wall  is  in  perfect  condition,  because  a  gap 
in  the  bridge  wall  might  cause  a  ' '  bag  ' '  in  the  boiler  by  concen- 
trating the  flames  on  one  spot. 

Never  allow  any  bare  places  on  the  grate,  nor  any  accumulation 
of  ashes,  or  dead  coal  in  the  corners  of  the  furnace,  as  such 
places  admit  great  quantities  of  cold  air  into  the  furnace,  and 
render  the  combustion  very  imperfect. 

In  firing  with  anthracite  coal,  do  not  poke  and  stir  up  the  fire, 
as  with  soft  coal,  but  let  it  alone. 

In  firing  soft  slack  coal,  fire  very  lightly  but  frequently,  carry- 
ing a  thin  fire. 

In  firing1  with  soft  lump  coal,  carry  a  thick  fire,  say  from  six 
to  eight  inches  deep,  according  to  the  size  of  the  furnace. 


HANDBOOK    ON    ENGINEERING.  535 

In  firing  up,  you  may  spread  the  fresh  coal  evenly  all  over  the 
grate,  or,  you  may  push  the  live  coals  back  towards  the  bridge- 
wall,  leavings  thin  bed  of  live  coals  near  the  furnace  doors,  and 
spreading  the  fresh  coal  on  top  of  it.  This  is  called  carrying  a 
coking  fire.  Some  prefer  the  one  and  some  the  other  method  of 
firing. 

In  case  you  should  find  the  water  in  the  boiler  out  of  sight, 
and  a  heavy  fire  in  the  furnace,  don't  get  rattled,  and  don't  lose 
your  head.  Open  the  furnace  doors,  and  close  the  ash-pit  doors, 
and  cover  the  fire  with  wet  ashes,  or  damp  clay,  completely 
smothering  it.  Let  everything  else  alone,  including  the  safety 
valve  and  the  engine.  Now  wait  until  the  boiler  cools  down  and 
the  gauge  shows  no  pressure,  then  turn  on  the  feed-water. 

On  the  other  hand,  if  there  is  but  very  little  fire  in  the  furnace, 
you  may  draw  the  fire,  instead  of  covering  it  with  ashes  or  clay. 

If  your  boiler  foams  badly  and  you  are  uncertain  as  to  the 
water  level,  stop  the  engine,  and  the  true  water  level  will  show 
itself  at  once. 

If  your  boiler  primes  and  water  is  carried  over  to  the  engine, 
it  shows  that  there  is  want  of  sufficient  steam  room  in  the  boiler. 
Either  put  a  dry-pipe  in  the  boiler,  or,  increase  the  steam  pressure 
if  the  boiler  will  safely  stand  it. 

Never  attempt  to  calk  a  leaky  seam  in  a  boiler  under  steam 
pressure,  because  the  jar  caused  by  the  hammer  blows  might 
cause  a  rupture  of  the  seam.  Better  to  be  on  the  safe  side 
always  when  repairs  are  required  in  a  steam  boiler,  and  wait  until 
the  boiler  is  cold.  The  above  applies  to  steam  pipes  and  valve 
casings,  also. 

Never  open  any  steam  valves  suddenly,  nor  close  them  sud- 
denly either,  because  it  is  highly  dangerous  to  do  so,  particularly 
if  there  is  considerable  water  in  the  pipes.  The  effect  is  the  same 
as  water  hammer  in  water  pipes. 

Smoke  is  caused  by  too  little  air  supply,  or  by  the  flames  being 


536  HANDBOOK    ON    ENGINEERING. 

prematurely  cooled.  Therefore,  after  firing  up  with  fresh  coal, 
it  might  be  necessary  to  leave  the  furnace  doors  ajar  in  order  to 
supply  sufficient  air  above  the  fuel. 

Remember  that  it  takes  nearly  24  cubic  feet  of  air  for  the 
proper  combustion  of  one  pound  of  soft  coal.  Hard  coal  does 
not  require  so  much. 

Each  and  every  boiler  in  a  battery  should  have  its  own  inde- 
pendent safety-valve  and  steam  gauge. 

If  you  are  obliged  to  force  your  fire,  watch  your  furnace  sheets 
for  indications  of  "  bagging,"  if  the  water  space  below  the  lowest 
row  of  tubes  is  cramped.  Water-tube  boilers  are  less  liable  to 
suffer  from  the  effects  of  forced  fires  than  shell  boilers. 

With  an  intensely  hot  fire  under  a  shell  boiler,  the  furnace 
sheets  are  liable  to  bag,  unless  there  is  ample  water  space  be- 
tween the  shell  of  the  boiler  and  the  bottom  row  of  tubes. 

The  use  of  mineral  oil  to  remove  or  prevent  boiler  scale,  is  not 
to  be  recommended.. 

Have  your  feed  water  analyzed,  and  use  a  scale  preventer 
adapted  to  its  requirements. 

By  all  means  endeavor  to  secure  a  steady  furnace  temperature, 
and  a  steady  steam  pressure,  for  herein  lies  much  economy  of 
fuel.  Fluctuations  are  wasteful. 

Put  a  damper  in  your  chimney  and  adjust  it  to  the  needs  of 
your  furnace.  Try  to  prevail  on  your  employer  to  put  in  a  shak- 
ing grate.  It  will  enable  you  to  carry  a  steady  furnace  temper- 
ature, and  also  enable  you  to  keep  the  air  spaces  in  your  grate 
free  and  open  without  breaking  up  your  fire. 

RULES  AND  PROBLEMS  RELATING  TO  STEAM  BOILERS. 

To  find  the  safe  working  pressure :  — 

U.  S*  Rule.  —  Multiply  one-sixth  (|)  of  the  lowest  tensile 
strength  found,  stamped  on  any  plate  in  the  cylindrical  shell, 


HANDBOOK  ON    ENGINEERING.  537 

by  the  thickness  —  expressed  in  inches  or  parts  of  an  inch  —  of 
the  thinnest  plate  in  the  same  cylindrical  shell,  and  divide  by  the 
radius  or  half  diameter  —  also  expressed  in  inches  —  and  the 
result  will  be  the  pressure  allowable  per  square  inch  of  surface 
for  single  riveting ;  to  which  add  20  per  cent  for  double  riveting, 
when  all  the  holes  have  been  "  fairly  drilled  "  and  no  part  of 
such  hole  has  been  punched.  . 

A.  S.  of  M.  E.  Rule.  —  First,  find  the  tensile  strength  of  the 
solid  plate  between  the  centers  of  two  adjacent  rivet  "holes.  Call 
this  factor  A. 

Next,  find  the  tensile  strength  of  the  solid  plate  between  the 
centers  of  two  adjacent  rivet  holes,  less  the  diameter  of  one  rivet 
hole.  Call  this  factor  13. 

Next,  find  the  shearing  strength  of  the  rivets.  Call  this 
factor  C. 

Now  divide  whichever  is  the  smaller  factor  13  or  C  by  A,  and 
the  quotient  will  give  the  strength  of  the  joint  as  compared  with 
the  solid  plate  —  expressed  as  a  percentage.  Then  multiply  the 
tensile  strength  of  the  plates  by  the  thickness  of  plates  —  in  frac- 
tional parts  of  an  inch  —  and  multiply  this  product  by  the  per- 
centage as  found  above,  and  divide  this  last  product  by  the 
radius  of  the  shell  in  inches,  and  the  quotient  will  be  the  bursting 
pressure. 

Divide  this  quotient  by  the  factor  of  safety  and  the  result  will 
give  the  safe  working  pressure. 

Example*  —  What  is  the  safe  working  pressure  for  a  steel 
boiler  60  inches  in  diameter,  with  side  seams  double  riveted, 
tensile  strength" of  plates  60,000  Ibs.  per  sqr.  in.,  thickness  of 
plate  |  inch.  Diameter  of  rivet  holes  £f  inch,  pitch  of  rivets  3J 
inches,  shearing  strength  of  rivets  38,000  Ibs.  per  sqr.  in.,  and 
factor  of  safety  5  ? 

Ans.  By  U.  S.  rule,  150  Ibs.  per  sqr.  in. 
By  A.  S.  of  M.  E.  rule,  106^  Ibs.  per.  sqr.  in. 


538  HANDBOOK    ON    ENGINEERING. 

Operation  by  U.  S.  rule:  — 

60,000 
-~-   =  10,000.     And,  10,000  X  |  =  3750. 

3750 
And,     -gjj-  =  125.     And,   125  X  .20  =25. 

Then,   125  +.25  =  150. 

Operation  by  A.  S.  of  M.  E.  rule:  — 
f"  =  .375". 

#"  =  .9375". 

Then,  60,000  X  3J  X  .375  —  73,125  Ibs.,  the  strength  of  the 
solid  plate  between  the  centers  of  two  adjacent  rivet  holes.  Call 
this  factor  A.  Also,  3J  =  3.25. 

Then,  3.25  —  .9375  =  2.3125. 

And,  60,000  X  2.3125  X  .375—52,031.25  Ibs.  the  strength 
of  the  plate  between-two  adjacent  rivet  holes.  Call  this  facto.r  B. 

Then,  .9375  X  -9375  X  .7854  =  .69029  of  a  square  inch,  the 
area  of  one  rivet  hole.  There  are  two  rows  of  rivets. 

Then,  .69029  X  2  =  1.38058  sqr.  ins.  the  area  of  two  rivet 
holes  combined. 

Then,  38,000  X  1.38058  =52,462.04  Ibs.,  the  resistance  of 
rivets  to  shearing.  Call  this  G.  Now  since  B  is  less  than  (7, 
divide  52,031.25  by  73,125  and  get  as  a  quotient  .71  +  ,  thus 
showing  the  strength  of  "the  joint  to  be  more  than  71  per  cent  of 
the  strength  of  the  solid  plates. 

Then,   60.000  X. 875  X. 71  _M9K  ^   per  sqr<   fa>|    the 

30 
bursting  pressure. 

And,    582'5  =   106.5   Ibs.  per   sqr.    in.,  the   safe    working 
5 

pressure. 


HANDBOOK    ON    ENGINEERING.  539 

To  find  the  horse  power  of  a  horizontal  return  tubular  boiler, 
from  its  heating  surface  :  — 

Rule*  —  Find  the  heating  surface  in  square  feet,  of  the  shell 
of  the  boiler,  measuring  from  one  fire  line  to  the  other.  Next 
find  the  internal  heating  surface  of  all  the  tubes  in  square  feet. 
Add  the  two  results  together  and  divide  their  sum  by  12,  and  the 
quotient  will  be  the  H.  P.  approximately.  The  heads  are 
omitted. 

Example* —  What  is  the  H.  P.  of  a  horizontal  return  tubular 
boiler  60  inches  in  diameter  and  20  feet  long,  with  44  four-inch 
tubes  each  20  feet  long,  the  distance  from  fire  line  to  fire  line 
being  9  feet?  Ans.  86.65  H.  P. 

Operation*  —  The  internal  diameter  of  a  4-inch  tube  is  3.732 
inches. 

Then,  20  X  9  =  180  square  feet  of  heating  surface  in  the 
shell. 

And,  8'782  X  3'1416  -B  .9770376   ft.,  the    circumference   of 
12 

one  tube  in  feet. 

And,  .9770376  X  20  X  44  =  859.793  -f  sqr.  ft.,  the  total 
heating,  surface  of  the  tubes. 

Then,   180+859.793  =  86.65  nearly. 
12 

To  find  the  factor  of  evaporation :  — 

Rule*  —  From  the  total  number  of  heat  units  in  one  pound  of 
steam  at  the  given  pressure,  subtract  the  number  of  heat  units  in 
one  pound  of  the  feed  water  at  its  given  temperature,  and  divide 
the  remainder  by  965.7,  which  is  a  constant. 

Example*  —  A  boiler  evaporates  6,000  Ibs.  of  water  per  hour 
from  feed-water  at  210  degrees  into  steam  at  125  Ibs.  gauge  pres- 


540  HANDBOOK    ON    ENGINEERING. 

sure,  what   is  the   equivalent  evaporation   ''from  and  at,"  and 
what  is  the  H.  P.  of  the  boiler? 

.  Ans.  Equiv.  evap.  6276  Ibs. 
H.  P.  182,  nearly. 

Operation*  —  The  total   number  of  heat  units  in  steam  at  125 
Ibs.  per  sqr.  in.  gauge  pressue  is  1221.5351. 

The  number  of  heat  units  in  feed-water  at  210  degrees 
equals  210.874.  The  latent  heat  of  steam  at  atmospheric  pres- 
sure, equals  965.7. 

Then,  1221.5351  —  210.874  =  1010.6611. 

And,  1  >1Q-6^11  =  1.046,  the  factor  of  evaporation. 
And,  6000  X  1-046  =  6276  the  equivalent  evaporation. 


Then,  =  181.9  H.  P. 

'   34.5 

To  find  how  many  pounds  of  steam  at  a  given  absolute  pressure 
will  flow  through  an  orifice  of  one  square  inch  area  in  one  sec- 
ond :  — 

Rule.  —  Divide  the  absolute  pressure  by  the  constant  number  70. 

Example.  —  How  many  pounds  of  steam  at  85  Ibs.  per  sqr.  in. 
gauge  pressure,  will  flow  through  an  orifice  one  inch  in  diameter, 
in  one  second  ?  Ans.  1.122  Ibs. 

Operation*  —  A  hole  1  inch  in  diameter  has  an  area  of  .7854 
of  a  sqr.  inch. 

And  85  +  15  =100  Ibs.  absolute. 

100  X  .7854 
Then,  ---  ^—  -=1.122. 

The  weight  of  a  cubic  foot  of  steam  at  100  Ibs.  per  sqr.  in. 

1.122 
absolute  pressure  is  .2307  of  a  pound.     Then,  -3307    ==  4t86    • 

cubic  feet. 


HANDBOOK    ON    ENGINEERING.  541 

To  find  the  width  of  a  reinforcing  ring  for  a  round  hole  in  a  flat 
surface,  when  the  ring  must  contain  as  many  square  inches  as 
were  cut  out  of  the  plate,  and  when  the  ring  and  the  plate  are  of 
the  same  thickness  :  — 

Rule*  —  Find  the  area  of  the  hole  in  square  inches  and  multi- 
ply it  by  2.  Divide  this  product  by  .7854  and  extract  the  square 
root  of  the  quotient  for  the  diameter  of  the  ring  over  all.  Sub- 
tract the  diameter  of  the  hole  from  the  diameter  over  all,  and 
divide  the  remainder  by  2  for  the  width  of  the  ring. 

Example*  —  What  should  be  the  width  of  a  reinforcing  ring  for 
a  hole  10  inches  in  diameter,  the  metal  cut  out,  and  the  metal  in 
the  ring  being  |  in.  thick?  Ans.  2T*g-  inches. 

Operation. —  10  X  10  X  .7854  =  78.54  sqr.  ins.  area  of  hole. 

And,  78.54  X  2  •=  157.08  sqr.  ins.  in  both  hole  and  ring. 
157.08 

And< 


And,    V200:^14-142+- 
And,    14.142—10=4.142. 

4.142 
Then,       ^      =  2.071"  or  practically 

To  find  the  width  of  a  reinforcing  ring  for  an  elliptical  manhole 
in  a  flat  surface,  when  the  ring  must  contain  as  many  square 
inches  as  are  contained  in  the  hole,  and  the  metal  cut  out  and 
metal  in  the  ring  are  of  the  same  thickness :  — 

Rule*  —  Square  the  short  diameter  of  the  hole  and  add  to  it  six 
times  the  short  diameter  multipled  by  the  long  diameter,  and  to 
this  product  add  the  square  of  the  long  diameter,  and  extract  the 
square  root  of  the  sum.  From  this  root  subtract  the  sum  of  the 
short  diameter  added  to  the  long  diameter,  and  divide  the  re- 
mainder by  4  for  the  width  of  the  ring. 

Example.  —  What  should  be  the  width  of  a  reinforcing  ring 
for  a  manhole  11"  X  15"?  Ans.  2  inches. 


542  HANDBOOK    ON    ENGINEERING. 

Operation.—  11"  X  H"  =  121. 

And,  11  X  15  X  6  =990. 

And,  15  X  15  =  225. 

Then,  121  +  990  +  225  =  1336. 

And,  V  1336  =  36.551. 

And,  11  +  15  =  26. 

Then,  36.551  —  26  =  10.551. 

10.551 
And,      —  T  —    =2.637  -f-  ins.  the  width  of  the  ring,  or,  prac- 


tically 2iJ  ins. 

Then,  2.637X2=5.274". 

And,  11  +  5.274  =  16.274"  short  diameter  of  ring  over  all. 

And,  15  -f  5.274  =  20.274"  long  diameter  over  all. 

Proof:    20.274  X  16.274  X  .7854=  259.13  +  square  inches 
area  of  hole  and  ring. 

And,  15  X  11  X  .'7854  =  129.59  +  sqr.  ins.  area  of  hole  alone. 

Then,  259.13—129.59  =  129.54. 


THE  AHOUNT  OF  STEAM  USED  WITH  VALVE  OPEN  WIDE, 
WITH  STEAH  JETS  AS  A  SMOKE  PREVENTIVE. 

STEAM    JETS. 

Given  two  boilers  with  separate  furnaces,  having  4  steam  jets 
in  each  furnace,  and  each  jet  T\  inch  in  diameter,  the  steam  pres- 
sure being  100  Ibs.  per  sqr.  inch  by  the  gauge.  How  many 
pounds  of  steam  at  this  pressure  will  flow  through  the  8  nozzles 
in  12  hours?  Answer.  1739  Ibs.  nearly. 

Operation :  TV"  =  .0625  ". 

Then,  .0625  X  -0625  X  .7854  =  .003067968750  sqr.  inch, 
area  of  1  jet. 


HANDBOOK    ON    ENGINEERING.  543 

And,  .003067968750  X  8  ==  .02454375  sqr.  inch,  the  com- 
bined area  of  8  jets. 

Also,  100  +  15  =  115  Ibs.  per  sqr.  inch,  the  absolute  steam 
pressure . 

And,   =  1.64   Ibs.  of  steam    per  second   that   will   flow 

70 

through  an  orifice  of  1  square  inch  area. 

Then,  1.64  X  .02454375  =  .04025175  Ibs.  of  steamier  second 
flowing  through  the  8  jets. 

Again:  There  are  43,200  seconds  in  12  hours. 
Thus:    12X60X60^43,200. 

Then,  .04025175  X  43,200  =  1738.8756  Ibs.  of  steam  will 
flow  through  8  jets  in  12  hours'  time. 

Taking  a  high  speed  automatic  cut-off  engine  using  20  Ibs.  of 
steam  per  H.  P.  per  hour,  the  8  steam  jets  would  waste  enough 
steam  in  12  hours  to  run  — 

A  10  H.  P.  engine  for  8%  hours. 
A  20      "         "      •  "   4J-       " 
A  40      "         "         "   2J        * 

An  80      "         "         "    1J*.     ' 

• 

Thus^lO  X- 20  =  200. 

-,     1739 

And.  _ =  81  nearly. 

200 

20  X  20  =  400. 

1739 
'    4QO~         *n       y' 

80  X  20  =  1600. 


544 


HANDBOOK    ON    ENGINEERING 


THE  STEAM  PUMP. 


CHAPTER     XIX 


The  Worthington  Compound  Pump. 

THE  WORTHINGTON  COMPOUND  PUMP. 

In  the  arrangement  of  steam  cylinders  here  employed,  the  steam 
is  used  expansively,  which  cannot  be  done  in  the  ordinary  form. 
Having  exerted  its  force  through  one  stroke  upon  the  smaller 
steam  piston,  it  expands  upon  the  larger  during  the  return  stroke, 
and  operates  to  drive  the  piston  in  the  other  direction.  This  is, 
in  effect,  the  same  thing  as  using  a  cut-off  on  a  crank  engine, 
only  with  the  great  advantage  of  uniform  and  steady  action  upon 
the  water. 


HANDBOOK    ON    ICNGINEERING. 


545 


Compound  cylinders  are  recommended  in  any  service  where 
the  saving  of  fuel  is  an  important  consideration.  In  such  cases, 
their  greater  first  cost  is  fully  justified,  as  they  require  30  to  33 
per  cent  less  coal  than  any  high-pressure  form  on  the  same  work. 


The   above   illustration    is    a  sectional  view  of  the  Worthington 

Compound  Pump  —  This  cut  shows  the  steam  valves 

properly   set. 


On  the  larger  sizes,  a  condensing  apparatus  is  often  added,  thus 
securing  the  highest  economical  results. 

Any  of  the  ordinary  forms  of  steam  pumps  can  be  fitted  with 
compound  cylinders. 

It  should  be  remembered  that,  as  the  compounds  use  less  steam 
their  boilers  may  be  reduced  materially  incize  and  cost,  compared 
with  those  required  by  the  high-pressure  form.  This  principle  of 
expansion  without  condensation  cannot  be  used  with  advantage 
wnere  the  steam  pressure  is  below  75  Ibs. 

35 


546 


HANDBOOK    ON    ENGINEERING 


The  Deane  Pump. 


The  above  is  a~  sectional  view  of  the 

DEANE  DIRECT  ACTING  STEAM  PUMP. 


The  operation  of  the  steam  valves*  —  In   the   Deane  Steam 
Pump  a  rotary  motion   is    not   developed   by  means  of  which  an 


HANDBOOK    ON    ENGINEERING. 


547 


eccentric  cnn  be  made  to  operate  the  valve.  It  is,  therefore, 
necessary  to  reverse  the  piston  by  an  impulse  derived  from  itself 
at  the  end  of  each  stroke.  This  cannot  be  effected  in  an  ordinary 
single-valve  engine,  as  the  valve  would  be  moved  only  to  the  cen- 
ter of-  its  motion,  and  then  the  whole  machine  would  stop.  To 
overcome  this  difficulty,  a  small  steam  piston  is  provided  to  move 
the  main  valve  of  the  engine.  In  the  Deane  Steam  Pump,  the 
lever  90,  which  is  carried  by  the  piston  rod,  comes  in  contact 


This  cut  shows  the  valves  properly  set. 


with  the  tappet  when  near  the  end  of  its  motion,  and  by  means 
of  the  valve-rod  24,  moves  the  small  slide-valve  which  operates 
the  supplemental  piston  9.  The  supplemental  piston,  carrying 
with  it  the  main  valve,  is  thus  driven  over  by  steam  and  the 
engine  reversed.  If,  however,  the  supplemental  piston  fails 
accidentally  to  be  moved,  or  to  be  moved  with  sufficient  prompt- 
ness by  steam,  the  lug  on  the  valve-rod  engages  with  it  and 
compels  its  motion  by  power  derived  from  the  main  engine. 


548 


HANDBOOK    ON    ENGINEERING, 


' 


SECTIONAL  VIEW  OF 

CAMERON"  STEAM  PUMP 


The  above  is  a  sectional  view  of  the  steam  end  of  a  Cameron 
pump. 

Explanation:  A.  is  the  steam  cylinder  ;  (7,  the  piston  ;  D,  the 
piston  rod  ;  Z/,  the-  steam  chest;  F,  the  chest  piston  or  plunger, 
the  right-hand  end  of  which  is  shown  in  section  ;  6r,  the  slide 
valve  ;  H,  a  starting  bar  connected  with  a  handle  on  the  outside  ; 
II  are  reversing  valves  ;  TT/rare  the  bonnets  over  reversing  valve 
chambers  ;  and  E  E  are  exhaust  ports  leading  from  the  ends  of 
steam  chest  direct  to  the  main  exhaust,  and  closed  by  the  revers- 
ing valve  II;  Nis  the  body  piece  connecting  the  steam  and  wau>v 


HANDBOOK    ON    ENGINEERING.  549 

Operation  of  the  Cameron  Pump:  Steam  is  admitted  to  the 
steam  chest,  and  through  small  holes  in  the  ends  of  the  plunger; 
F  fills  the  spaces  at  the  ends  and  the  ports  E  E  as  far  as  the 
reversing  valves  //;  with  the  plunger  F  and  slide  valve  G  in 
position  to  the  right  (as  shown  in  cut),  steam  would  be  admitted 
to  the  right-hand  end  of  the  steam  cylinder  -A,  and  the  piston  C 
would  be  moved  to  the  left.  When  it  reaches  the  reversing  valve 
I  it  opens  it  and  exhausts  the  space  at  the  left-hand  end  of  the 
plunger  F,  through  the  passage  E ;  the  expansion  of  steam  at  the 
right-hand  end  changes  the  position  of  the  plunger  F,  and  with  it 
the  slide  valve  G,  and  the  motion  of  the  piston  C  is  instantly 
reversed.  The  operation  repeated  makes  the  motion  continuous. 
In  its  movements,  the  plunger  F  acts  as  a  slide  valve  to  shut  off 
the  ports  E  E,  and  is  cushioned  on  the  confined  steam  between 
the  ports  and  steam  chest  cover.  The  reversing  valves  /  /  are 
closed  immediately  the  piston  C  leaves  them ,  by  pressure  of  steam 
on  their  outer  ends,  conveyed  direct  from  the  steam  chest. 

Operation.  —  Supposing  the  steam  piston  C  moving  from  right 
to  left:  When  it  reaches  the  reversing  valve  I  it  opens  it  and 
exhausts  the  space  on  the  left-hand  end  of  the  plunger  F,  through 
the  passage  E,  which  leads  to  the  exhaust  pipe  ;  the  greater  pres- 
sure inside  of  the  steam  chest  changes  the  position  of  the  plunger 
F  and  slide  valve  G,  and  the  motion  of  the  piston  C  is  instantly 
reversed.  The  same  operation  repeated  at  each  stroke  makes  the 
motion  continuous.  The  reversing  valves  //are  closed  by  a  pres- 
sure of  steam  on  their  large  ends,  conveyed  by  an  unseen  passage 
direct  from  the  steam  chest.  When  a  pump  is  first  connected, 
remove  the  bonnets  K  K  and  valves  /  /  and  blow  steam  through 
to  remove  any  dirt,  oil  or  gum  that  may  be  lodged  in  the  steam 
ports.  Take  valve  F,  valve  G  and  //  out  and  wipe  off  with 
clean  waste,  and  then  oil  and  put  back.  Then  see  that  the  pack- 
ing is  not  too  tight.  When  a  Cameron  pump  has  been  run  a  long 
time,  the  plunger  F  becomes  worn  and  leaks  enough  steam  tQ 


550 


HANDBOOK    ON    ENGINEERING. 


cause  the  valve  F  to  become  balanced.  The  effect  of  this  is,  the 
pump  will  remain  on  the  end  ;  to  overcome  this,  take  out  plunger 
F,  or  piston,  as  it  is  called  by  some,  and  drill  the  little  hole  that 
you  will  find  in  the  ends  of  same  a  little  larger,  say  about  one- 
fourth  larger ;  that  will  increase  the  pressure  on  both  ends  of 
plunger  F ' ;  as  soon  as  the  piston  comes  in  contact  Avith  valve  1 
the  steam  is  exhausted  to  exhaust  pipe. 


30-* 


The  above  is  a  sectional  cut  of 

THE  KNOWLES  DIRECT  ACTING  STEAH  PUMP. 

Explanation  of  steam  valves,  etc.  —  The  Knowles,  in  fact,  all 
first-class  direct  acting  steam  pumps,  is  absolutely  free  from  what 
is  termed  a  "  dead  center,"  when  in  first-class  order. 

This  feature  in  the  Knowles  Pump  is  secured  by  a  very  simple 
and  ingenious  mechanical  arrangement,  i.  e.,  by  the  use  of  an 
auxiliary  piston  which  works  in  the  steam  chest  and  drives  the 
main  valve.  This  auxiliary  or  "  chest  piston,"  as  it  is  called,  is 
driven  backward  and  forward  by  the  pressure  of  steam,  carrying 


HANDBOOK    ON    ENGINEERING. 


551 


with  it  the  main  valve,  which  valve,  in  turn,  gives  steam  to  the 
main  steam  piston  that  operates  the  pump.  This  main  valve  is  a 
plain  slide  valve  of  the  B  form,  working  on  a  Hat  seat.  The  chest 
piston  is  slightly  rotated  by  the  valve  motion  ;  this  rotative  move- 
ment places  the  small  steam  ports,  I),  E,  F  (which  are  located  in 


The  Knowles  Direct  Acting  Steam  Pump. 

the  under  side  of  the  said  chest  piston),  in  proper  contact  with 
corresponding  ports  A  B  cut  in  the  steam  chest  No.  31.  The 
steam  entering  through  the  port  at  one  end:  and  filling  the  space 
between  the  chest  piston  and  the  head,  drives  the  said  piston  to 
the  end  of  its  stroke  and,  as  before  mentioned,  carries  the  main 
slide  valve  with  it.  When  the  chest  piston  has  traveled  a  certain 
distance,  a  port  on  the  opposite  end  is  uncovered  and  steam  there 
enters,  stopping  its  further  travel  by  giving  it  the  necessary 


552 


HANDBOOK    ON    ENGINEERING. 


cushion.  In  other  words,  when  the  rotation  motion  is  given  to 
the  auxiliary  or  valve  driving  piston  by  the  mechanism  outside, 
it  opens  the  port  to  steam  admission  on  one  end,  and  at  the  same 
time  opens  the  port  on  the  other  end  to  the  exhaust. 


'•is 


This  cut  shows  the  valves  properly  set. 

Operation  of  the  Knowles  Pump  is  as  follows :  The  piston  rod, 
with  the  tappet  arm,  moves  backward  and  forward  from  the 
impulse  given  by  the  steam  piston.  At  the  lower  part  of  this 
tappet  arm  is  attached  a  stud  or  bolt,  on  which  there  is  a  friction 
roller.  This  roller  coming  in  contact  with  the  "  rocker  bar"  at 
the  end  of  each  stroke,  operates  the  latter.  The  motion  given  the 
"  rocker  bar  "  is  transmitted  to  the  valve  rod  by  means  of  the 
connection  between,  causing  the  valve  rod  to  partially  rotate. 
This  action,  as  mentioned  above,  operates  the  chest  piston,  which 
carries  with  it  the  main  slide  valve,  the  said  valve  giving  steam  to 
the  main  piston.  The  operation  of  the  pump  is  complete  and 


HANDBOOK    ON    ENGINEERING.  553 

continuous.  The  upper  end  of  the  tappet  arm  does  not  come  in 
contact  with  the  tappets  on  the  valve  rod,  unless  the  steam  pres- 
sure from  any  cause,  should  fail  to  move  the  chest  piston,  in  which 
case  the  tappet  arm  moves  it  mechanically. 

NOTICE. 

1.  Should  the  pump  run  longer  stroke  one  way  than  the  other, 
simply  lengthen  or  shorten   the  rocker  connection  (part  25)  so 
that  rocker  bar  (part  23)  will  touch  rocker  roller  (20)  equally 
distant  from  center  (22). 

2.  Should  a  pump  hesitate  in  making  its  return  stroke,  it  is  be- 
cause rocker  roller  (20)  is  too  low  and  does  not  come  in  contact 
with  the  rocker  bar   (23)   soon  enough.     To  raise  it,  take  out 
rocker  roller  stud  (20 A),  give  the  set  screw  in  this  stud  a  suffi- 
cient downward  turn,  and  the  stud  with  its  roller  may  at  once  be 
raised  to  proper  height. 

o.  Should  valve  rod  (77)  ever  have  a  tendency  to  tremble, 
slightly  tighten  up  the  valve  rod  stuffing  box  nut  (28).  When 
the  valve  motion  is  properly  adjusted,  tappet  tip  (16)  should 
not  quite  touch  collar  (15)  and  clamp  (27).  Rocker  roller 
(20),  coming  in  contact  with  rocker  bar  (23)  will  reverse  the 
stroke. 

Operation  and  construction  of  the 

HOOKER  DIRECT-ACTING  STEAM=PUMP. 

The  parts  being  in  position,  as  shown,  the  steam  on  being  ad- 
mitted to  the  center  of  the  valve  chamber,  brings  its  pressure  to 
bear  on  the  main  and  supplemental  flat  slide  valve  4  and  7,  and 
also  within  the  recess  in  the  center  of  the  supplemental  piston  6. 
The  recess  incloses  the  main  valve  4,  so  that  this  valve  will  move 
with  the  supplemental  piston  whenever  the  steam  is  supplied  to 


554 


HANDBOOK    ON    ENGINEERING. 


and  exhausted  from  each  end  of  this  piston.  The  live  steam 
passes  through  the  left-hand  ports  A1  U1,  driving  the  main  piston 
2  to  the  right,  and  the  exhaust  passes  out  through  the  right-hand 
ports  A  and  C  under  the  cavity  in  the  main  valve  4  to  the  atmos- 
phere. As  the  main  piston  nears  the  right  hand  port,  the  valve 
lever  13,  which  is  attached  to  the  piston  rod  3,  brings  the  dog  1 7, 
in  plate  16,  in  contact  with  the  valve  arm  _Z£,  and  moves  the  sup- 
plemental valve  7  to  the  right,  thus  supplying  live  steam  to  the 


right  of  the  supplemental  piston  6',  and  exhausting  from  the  left 
through  the  ports  e  e.  As  the  supplemental  piston  incloses  the 
main  valve,  this  valve  is  carried  with  it  to  the  left.  Steam  now 
enters  the  right-hand  ports  A  B  and  is  exhausted  from  the  left- 
hand  main  port  A.  The  engine  commences  its  return  stroke  and 
the  operation  just  described  becomes  continuous.  As  the  main 
piston  (2)  closes  the  main  port  (A)  to  the  right,  it  is  arrested  on 
compressed  exhaust  steam.  The  main  valve  4  having  closed  the 
auxiliary  ports  (B)  leading  to  that  end  of  the  main  cylinder,  the 


HANDBOOK    ON    ENGINEERING. 


555 


This  cut  shows  the  steam  valves  properly  set. 

steam  being   supplied  through  both  the  main  and  auxiliary  ports, 
but  released  through  the  main  ports  only. 


BLAKE  STEAM  PUHP. 

Description  of  the  Blake  Steam  Pump*  —  The  Blake  Steam 

Pump  is  absolutely  positive  in  its  action ;  that  is  to  say,  the 
operation  at  the  slowest  speed  under  any  pressure,  is  perfectly 
continuous,  and  the  pump  is  never  liable  to  stop  as  the  main  valve 
passes  its  center,  if  the  pump  is  in  good  order.  An  ingenious  and 
simple  arrangement  is  used  in  the  Blake  Pump  to  overcome  the 
"  dead  center,"  as  will  be  seen  from  the  engravings. 

Operation  of  the  Blake  Steam  Pump*  —  The  main  or  pump 
driving  piston  A  could  not  be  made  to  work  slowly  were  the 
main  valve  to  derive  its  movement  solely  from  this  piston  ;  for 


556 


HANDBOOK    ON    ENGINEERING. 


when  this  valve  had  reached    the   center  of    its  stroke,  in    which 
position  the  ports  leading  to  the  main  cylinder  would  be  closed, 


The  Blake  Steam  rump. 

no  steam  could  enter  the  cylinder  to  act  on  said  piston,  con- 
sequently, the  latter  would  come  to  rest,  since  its  momentum 
would  be  insufficient  to  keep  it  in  motion,  and  the  main 
valve  would  remain  in  its  central  position  or  kt  dead  cen- 
ter." To  shift  this  valve  from  its  central  position  and 
admit  steam  in  front  of  the  main  piston  (whereby  the  motion 
of  the  piston  is  reversed  and  its  action  continued),  some  agent 
independent  of  the  main  piston  must  be  used.  In  the  Blake 
Pump,  this  independent  agent  is  the  supplemental  or  valve-driving 
piston  B.  The  main  valve,  which  controls  the  admission  of  steam 
to,  and  the  escape  of  steam  from,  the  main  cylinder,  is  divided 
into  two  parts,  one  of  which,  (7,  slides  upon  a  seat  on  the  main 
cylinder,  and,  at  the  same  time,  affords  a  seat  for  the  other  part, 


HANDBOOK    ON    ENGINEERING. 


557 


D,  which  slides  upon  the  upper  face  of  C.  As  shown  in  the  en- 
graving, D  is  at  the  left-hand  end  of  its  stroke,  and  C  at  the 
opposite,  or  right-hand  end  of  its  stroke.  Steam  from  the  steam- 
chest  J  is,  therefore,  entering  the  right-hand  end  of  the  main 
cylinder  through  the  ports  E  and  //,  and  the  exhaust  is  escap- 
ing through  the  ports  Hl  and  E1,  K  and  M,  which  causes  the 


Sectional  views  of  steam  cylinder,  valves,  etc., 
of  the  Blake  Steam  Pump. 

main  piston  A  to  move  from  right  to  left.     When  this  piston  has 
nearly  reached  the  left-hand  end  of  its  cylinder  the  valve  motion 


558 


HANDBOOK    ON    ENGINEERING. 


(not  shown)  moves  the  valve-rod  7J,  and  this  causes  C,  together 
with  its  supplemental  valve  11  and  S  81  (which  form,  with  (1,  one 
casting)  to  be  moved  from  right  to  left.  This  movement  causes 
steam  to  be  admitted  to  the  left-hand  end  of  the  supplemental 
cylinder,  whereby  its  piston  11  will  be  forced  toward  the  right, 
carrying  D  with  it  to  the  opposite  or  right-hand  end  of  its  stroke  ; 
for  the  movement  of  /Sy  closes  N  (the  steam  port  leading  to  the 


This  cut  shows  the  valves  properly  set. 

right-hand  end),  and  the  movement  of  S1  opens  Nl  (the  port 
leading  to  the  opposite,  or  left-hand  end).  At  the  same  time  the 
movement  of  0  opens  the  right-hand  end  of  the  cylinder  to 
the  exhaust  through  the  exhaust  ports  X  and  Z.  The  ports  C 
and  D  now  have  positions  opposite  to  those  shown  in  the  engrav- 
ings, and  steam  is,  therefore,  entering  the  main  cylinder  through 
the  ports  El  and  Hl,  and  escaping  through  the  ports  //,  E,  K 
and  Jf,  which  will  cause  the  main  piston  A  to  move  in  the  op- 


HANDBOOK    ON    ENGINEERING.  559 

posite  dhvction,  or  from  left  to  right,  and  operations  similar  to 
those  already  described  will  follow,  when  the  piston  approaches 
the  right-hand  end  of  its  cylinder.  By  this  simple  arrangement 
the  pump  is  rendered  positive  in  its  action  ;  that  is,  it  will  in- 
stantly start  and  continue  working  the  moment  steam  is  admitted 
to  the  steam  chest.  The  main  piston  A  cannot  strike  the  head  of 
the  cylinder,  for  the  main  valve  has  a  head ;  or,  in  other  words, 
steam  is  always  admitted  in  front  of  said  piston  just  before  it 
reaches  either  end  of  its  cylinder,  even  should  the  supplemental 
piston  B  be  tardy  in  its  action  and  remain  with  D  at  that  end, 
toward  which  the  piston  A  is  moving  ;  for  C  would  be  moved  far 
enough  to  open  the  steam  port  leading  to  the  main  cylinder,  since 
the  possible  travel  of  C  is  greater  than  that  of  D.  The  supple- 
mental piston  B  cannot  strike  the  heads  of  its  cylinders,  for  in  its 
alternate  passage  beyond  the  exhaust  ports  X  and  X,  it  cushions 
on  the  vapor  intrapped  in  the  ends' of  this  cylinder. 

MISCELLANEOUS  PUHP  QUESTIONS. 

Q.  What  is  a  pump?  A.  It  is  hard  to  get  a  definition  that 
will  cover  the  whole  ground.  A  pump  may  be  said  to  be  a 
mechanical  contrivance  for  raising  or  transferring  fluids  ;  and  as  a 
general  thing  consists  of  a  moving  piece  working  in  a  cylinder  or 
other  cavity ;  the  device  having  valves  for  admitting  or  retaining 
the  fluids. 

Q.  What  two  classes  of  operations  are  included  in  the  term 
"raising"  fluids?  A.  They  may  be  raised  by  drafting  or  suc- 
tion, from  their  level  to  that  of  the  pump ;  they  may  be  raised 
from  the  level  of  the  pump  to  a  higher  level. 

Q.  Do  pumps  always  "raise"  by  either  method,  from  one 
level  to  a  higher  one,  the  liquid  which  they  transfer?  A.  No  ;  in 
many  cases  the  liquid  flows  by  gravity  to  the  pump ;  and  in  some 
it  is  delivered  at  a  lower  level  than  that  at  which  it  is  received. 


560  HANDBOOK    ON    ENGINEERING. 

Q.  Where  a  pump  is  not  used  for  raising  a  liquid  to  a  higher 
level,  for  what  is  it  generally  used?  A.  To  increase  or  decrease 
its  pressure. 

Q.  What  classes  of  liquids  are  handled  by  pumps  ?  A.  Air, 
ammonia,  lighting  gas,  oxygen,  etc. 

Q.  Name  some  liquids  which  are  handled  by  pumps?  A. 
Water,  brine,  beer,  tan  liquor,  molasses,  acids  and  oils. 

Q.  Where  it  is  not  specified  whether  a  pump  is  for  gas  or  for 
liquid,  which  is  generally  understood?  A.  Liquid. 

Q.  What  gas  is  most  frequently  pumped?     A.  Air. 

Q.  What  liquid  is  generally  understood  if  none  other  is  speci- 
fied for  a  pump?  A.  Water. 

Q.  Can  pumps  handle. hot  and  cold  liquids?  A.  Yes;  though 
cold  are  easier  handled  than  hot. 

Q.  What  is  the  difference  between  a  fluid  and  a  liquid?  A. 
Every  liquid  is  a  fluid  ;  every  fluid  is  not  a  liquid.  Air  is  a  fluid  ; 
water  is  both  a  fluid  .  and  a  liquid.  Every  liquid  can  be  poured 
from  one  vessel  to  another. 

SUCTION. 

Q.  What  causes  the  water  to  rise  in  a  pump  by  so-called 
suction?  A.  The  unbalanced  pressure  of  the  air  upon  the  surface 
of  the  liquid  below  the  pump,  forces  the  water  up  into  the  suction 
pipe  when  the  piston  is  withdrawn  from  the  liquid. 

Q.  How  much  is  the  pressure  of  the  atmosphere ?  A.  At  the 
sea  level  about  14.71bs.  per  square  inch,  or  2116.8  Ibs.  per  square 
foot. 

Q.  In  what  direction  is  this  pressure  exerted ?  A.  In  every 
direction  equally. 

Q.  What  tends  to  prevent  the  water  from  being  lifted?  A. 
The  force  of  gravity,  which  is  the  result  of  the  attraction  of  the 
earth's  center. 


HANDBOOK    ON    ENGINEERING.  5 HI 

Q.  In  what  direction  does  the  force  of  gravity  act?  A.  In 
radial  lines  towards  the  center  of  the  earth. 

Q.  With  what  force  does  this  gravity  act?  A.  That  depends 
upon  the  substance  upon  which  it  is  acting. 

Q.  Why  do  you  refer  to  the  level  of  the  sea  in  speaking  of  the 
pressure  of  the  air  and  the  weight  of  water?  A.  Because  the  air 
pressure  becomes  less  as,  in  rising  above  the  sea  level,  we  recede 
from  the  center  of  the  earth,  and  the  weight  of  a  given  quantity 
of  water  or  any  other  substance  becomes  less  than  it  is  at  the  level 
of  the  sea,  as  we  approach  to  or  recede  from  the  center  of  the 
earth. 

Q.  How  is  it  that  the  weight  of  any  substance  becomes  less  if 
you  go  either  above  or  below  the  sea  level?  A.  The  farther  you 
go  from  the  earth,  the  less  its  attraction  and  the  less  a  given 
body  will  weigh  upon  a  spring  balance.  The  farther  down  into 
the  earth  you  go,  the  nearer  you  get  to  the  center  of  the  earth,  at 
which,  there  being  attraction  upon  all  sides,  any  body  would 
weigh  nothing.  Going  from  the  surface  of  the  earth  towards  its 
center,  then,  a  body  weighs  less  and  less  upon  a  spring  balance. 

Q.  Why  do  you  specify  a  spring  balance?  A.  Because  in 
weighing  by  counterpoise,  both  the  body  to  be  weighed  and  the 
counterpoise  by  which  it  is  weighed,  would  change  their  weights 
in  the  same  proportion,  as  the  position  with  regard  to  the  center 
of  the  earth  was  changed. 

Q.  What  are  the  causes  which  principally  prevent  pumps  from 
lifting  up  to  the  normal  maximum?  A.  Friction  ;  leakage  of  air 
into  the  suction,  chokes  in  the  suction  pipe. 

Q.  Can  a  liquid  be  "drafted"  without  the  expenditure  of 
work  ?  A.  No  ;  in  drafting  a  liquid  to  the  full  height  to  which  it 
can  be  drafted,  at  least  as  much  power  must  be  expended  as, 
would  lift  the  same  weight  of  liquid  that  height  by  any  mechan- 
ical means  ;  only  the  amounts  of  friction  being  different. 

Q.  Then  what  advantage  is  there  in  having  a  pump  draft  its 

36 


562  HANDBOOK    ON    ENGINEERING. 

water  to  the  fall  possible  height,  over  having  it  force  the  water 
the  full  height?  A.  Convenience  in  having  the  pump  higher  up. 

Q.  Can  a  pump  throw  water  higher  or  farther,  with  a  given 
expenditure  of  power,  where  it  flows  in,  than  where  it  must  draft 
its  water?  A.  Yes;  on  the  same  principle  that  it  can  throw 
farther  or  force  harder  when  the  water  is  forced  to  its  suction 
side  than  where  it  merely  flows  in. 

Q.  What  is  the  use  of  the  suction  chamber?  A.  To  enable 
the  pump  barrel  to  fill  where  the  speed  is  high;  to  prevent 
pounding,  when  the  pump  reverses. 

Q.  Upon  what  does  the  lifting  capacity  of  a  pump  depend? 
A.  When  the  pump  is  in  good  order  its  lifting  capacity  depends 
mainly  upon  the  proportion  of  clearance  in  the  cylinder  and  valve 
chamber  to  the  displacement  of  the  piston  and  plunger. 

Q.  Which  will  lift  further,  an  ordinary  piston  pattern  pump  or 
a  plunger  pump?  And  why?  A.  Other  things  being  as  nearly 
equal  as  they  can  be  made  between  these  two  pumps,  the  piston 
pump  will  lift  the  farther  of  the  two,  because  the  plunger  pump 
has  the  most  clearance. 

Q.  What  is  the  advantage  of  the  suction  chamber?  A.  To 
assist  the  pump  in  drafting,  especially  at  high  speed. 

Q.  What  is  the  advantage  of  the  air  chamber?  A.  To  make 
the  stream  steady. 

Q.  What  difficulty  isv  sometimes  met  with  in  using  an  air 
chamber?  A.  Where  the  pressure  is  very  great  sometimes  the 
air  is  absorbed  by  the  water,  and  thus  the  cushion  is  detroyed. 

FORCING. 

Q.  What  will  be  the  volume  of  the  air  in  the  air  chamber  of  a 
force  pump,  when  the  pump  is  forcing  against  a  head  of  67.6 
feet?  A.  It  will  be  reduced  to  half  its  ordinary  volume,  because 
it  will  be  at  the  pressure  of  two  atmospheres. 


HANDBOOK    OX    ENGINEERING. 


563 


The  above  cut  shows  a  pump  with  a  removable  cylinder 
or  liner,  and  is  packed  with  fibrous  packing  set  out  by  adjustable 
set  screws  and  nuts.  This  style  of  a  pump  is  the  best  for  small 
water-works  or  elevators,  or  where  a  pump  is  used  where  the 
water  is  muddy  or  sandy. 

To  find  the  horse  power  necessary  to  elevate  water  to  a 
given  height :  Multiply  the  total  weight  of  the  water  in  pounds 
by  the  height  in  feet  and  divide  the  product  by  33,000  (an  allow- 
ance of  25  per  cent  should  be  added  for  water  friction,  and  a  further 
allowance  of  25  per  cent  for  loss  in  steam  cylinder.) 

The  heights  to  which  pumps  will  force  water  when  running  at 


564  HANDBOOK    ON    ENGINEERING. 

100  feet  piston  speed  per  minute,  and  the  suction  and  discharge 
pipes  being  of  moderate  length,  will  be  found  by  dividing  the  area 
of  the  steam  piston  by  the  area  of  the  water  piston,  and  multi- 
plying the  quotient  by  the  steam  pressure.  Deduct  40  per  cent 
for  friction  and  divide  the  remainder  by  .434. 

Example*  —  To  what  height  will  an  8-inch  steam  piston,  with 
a  5-inch  water  piston,  force  water,  the  steam  pressure  being  80 
Ibs.  by  gauge?  .Ans.  283  ft.  nearly. 

Operation.  —  Area  of  steam  piston  =  50. 2G  sq.  ins. 
'4      "  water       "       — 19.63    "      " 

Then,   — ^  =  2.56.     And  2.50  X  80  =  204.80  Ibs. 

iy.63  , 

Then,  204.80  less  40%  =      122.88  Ibs. 

1  22  HH 
And,         '      =  283  -f  feet. 

An  allowance  must  be  made  where  long  pipes  are  used. 

The  normal  speed  of  pumps  is  taken  at  100  piston  feet  per 
minute,  which  speed  can  be  considerably  increased  if  desired. 

For  feeding1  boilers,  a  speed  of  25  to  50  piston  feet  per  minute 
is  most  desirable. 

A  gallon  of  water,  U.  S.  Standard,  weighs  8£  Ibs.  and  contains 
231  cubic  inches. 

A  cubic  foot  of  water  weighs  62.425  Ibs.  and  contains  1,728 
cubic  inches,  or  7J  gallons. 

Doubling  the  diameter  of  a  pipe  increases  its  capacity  four 
times. 

Friction  of  liquids  in  pipes  increases  as  the  square  of  the 
velocity. 

To  find  the  area  of  a  piston,  square  the  diameter  and  multiply 
by  .7854. 


HANDBOOK    ON    ENGINEERING.  565 

Boilers  require,  for  eacli  nominal  horse-power,  about  one  cubic 
foot  of  feed  water  per  hour. 

In  calculating  horse  power  of  tubular  or  flue  boilers,  consider 
15  square  feet  of  heating  surface  equivalent  to  one  nominal  horse- 
power. 

To  find  the  pressure  in  pounds  per  square  inch  of  a  column 
of  water,  multiply  the  height  of  a  column  in  feet  by  .434. 
Approximately,  we  say  that  every  foot  of  elevation  is  equal  to 
one-half  Ib.  pressure  per  square  inch ;  this  allows  for  ordinary 
friction. 

The  area  of  the  steam  piston,  multiplied  by  the  steam  pressure, 
gives  the  total  amount  of  pressure  that  can  be  exerted.  The 
area  of  the  water  piston,  multiplied  by  the  pressure  of  water  per 
square  inch,  gives  the  resistance.  A  margin  must  be  made 
between  the  power  and  the  resistance  to  move  the  pistons  at  the 
required  speed  —  say  from  20  to  40  per  cent,  according  to  speed 
and  other  conditions. 

To  find  the  capacity  of  a  cylinder  in  gallons :  Multiplying  the 
area  in  inches  by  the  length  of  stroke  in  inches  will  give  the  total 
number  of  cubic  inches  ;  divide  this  amount  by  231  (which  is  the 
cubical  contents  of  a  gallon  of  water)  and  quotient  is  the  capacity 
in  gallons. 

To  find  quantity  of  water  elevated  in  one  minute  running  at  100 
feet  of  piston  speed  per  minute :  Square  the  diameter  of  water 
cylinder  in  inches  and  multiply  by  4. 

Example:  Capacity  of  a  five-inch  cylinder  is  desired.  The 
square  of  the  diameter  (5  inches)  is  25,  which,  multiplied  by  4, 
gives  100,  which  is  gallons  per  minute,  approximately. 

Q.  "  What  is  the  reason  that  a  steam  pump  of  the  horizontal 
double  acting  type  should  throw  an  intermitting  stream  under 
pressure,  like  the  stream  from  milking  a  cow,  only  not  quite  so 
bad  as  that?  1  have  tried  valves  of  different  sizes,  with  different 
amount  of  rise,  springs  or  valves  of  different  tension,  different 


566  HANDBOOK    ON    ENGINEERING. 

kinds  of  packing  in  water  piston,  .and  different  sized  water  ports 
or  passages,  without  any  apparent  difference."  A.  Steam  pumps 
of  the  horizontal  double-acting  type  are  not  alone  in  throwing  an 
intermitting  stream.  The  same  thing  shows  up  in  vertical  single- 
acting  pumps  ;  and  all  horizontal  double-acting  pumps  do  not  so 
behave.  The  steam  fire  engine  shows  that  no  type  of  pump  is 
exempt  from  •'  squirting/' 

Q.  How  may  this  squirting  be  lessened?  A.  By  increasing 
the  suction  valve  area ;  by  giving  more  suction  chamber  and 

more  air  chamber. 

##'*  *  *  *  *  #  * 

Q.  What  is  a  sinking  pump?  A.  One  which  can  be  raised  and 
lowered  conveniently,  for  pumping  out  drowned  mines,  etc, 

Q.  Into  what  main  general  classes  may  reciprocating  cylinder 
pumps  be  divided?  A.  Into  single  acting  and  double  acting. 

Q.  What  is  a  single  acting  reciprocating  pump?  A.  One  in 
which  each  reciprocation  or  single  stroke  in  one  direction  causes 
one  influx  of  fluid,  and  each  reciprocation  or  single  stroke  in  the 
opposite  direction  causes  one  discharge  of  fluid.  In  other  words, 
the  pump,  as  regards  its  action,  is  single  ended. 

Q.  What  is  a  double  acting  reciprocating  pump?  A.  One  in 
which  each  end  acts  alternately  for  suction  and  discharge.  Re- 
ciprocation of  the  piston  in  one  direction  causes  an  influx  of 
fluid  into  one  end  of  the  pump  from  the  source,  and  a  discharge 
of  fluid  at  the  opposite  end ;  on  the  return  stroke  the  former 
suction  end  becomes  the  discharge  end.  In  other  words,  the 
pump  is  double  ended  in  its  action  ;  or  is  'l  double-acting." 

Q.  What  is  the  special  advantage  of  having  double-acting 
pump  cylinders?  A.  The  column  of  water  is  kept  in  motion 
more  constantly,  and  hence  there  is  less  jar ;  smaller  pipes  may 

be  used. 

**#          *          *          *          *  *          *          *  N        .$ 

Q.  How  may  those  pumps  which  are  driven  by  steam  against  a 


HANDBOOK    ON    ENGINEERING.  567 

steam  piston  be  divided  ?  A.  Into  those  which  have  a  fly  wheel 
and  those  which  have  no  fly  wheel. 

Q.  Into  what  classes  may  those  pumps  which  are  driven  by 
steam,  without  a  flywheel,  be  divided?  A.  Into  direct  acting 
and  duplex. 

Q.  What  is  the  advantage  of  a  fly  wheel  steam  pump?  A. 
Steadiness  of  action ;  the  capability  of  using  the  steam  expan- 
sively. 

Q.  What  are  the  disadvantages  of  fly  wheel  pumps?  A.  Great 
weight ;  inability  to  run  them  very  slowly  without  gearing  down 
from  the  fly  wheel  shaft,  as  the  wheel  must  run  comparatively 
rapidly. 

Q.  What  is  a  direct-acting  steam  pump?  A.  One  in  which 
there  is  no  rotary  motion,  the  piston  being  reversed  by  an  impulse 
derived  from  itself  at  or  near  the  end  of  each  stroke.  There  is 
but  one  steam  cylinder  for  one  water  cylinder ;  the  valve  motion 
of  the  steam  cylinder  being  controlled  by  the  action  of  the  steam 
in  that  cylinder. 

HOW  TO  SET  THE  STEAfl  VALVES  ON  A  DUPLEX  PUMP. 

• 
The  steam  valves  on  Duplex  pumps  generally  have  no  outside 

lap,  consequently,  when  in  its  central  position,  it  just  covers  the 
steam  ports  leading  to  the  opposite  ends  of  cylinder. 

By  lost  motion  is  meant,  the  distance  a  valve-rod  travels 
before  moving  the  valve;  if  the  steam-chest  cover  is  off  the 
amount  of  lost  motion  is  shown  by  the  distance  the  valve  can  be 
moved  back  and  forth  before  coming  in  contact  with  the  valve- 
rod  nut.  The  object  of  lost  motion  is  to  allow  one  pump  to 
almost  complete  its  stroke  before  moving  the  valve  of  its  fellow 
engine.  As  the  steam  piston  is  nearing  the  end  of  its  stroke,  it 
moves  the  valve  of  its  fellow  engine,  admitting  steam  and  start- 
ing its  fellow  engine  as  it  lays  down  its  own  work  ;  in  other  words, 


568 


HANDBOOK    ON    ENGINEERING. 


the  other  picks  it  up.  The  amount  of  lost  motion  required  is 
enough  to  allow  each  piston  to  complete  its  stroke  ;  in  other  words, 
if  there  was  no  lost  motion,  as  each  piston  would  pass  the 
center  of  their  travel,  they  would  move  the  valve  of  their 
fellow  engine,  and  the  result  would  be  a  very  short  stroke. 


This  cut  shows  the  steam  valves  properly  set. 

To  set  the  steam  valves,  move  the  steam  piston  towards  the 
steam  cylinder  head  until  it  comes  in  contact  with  the  head  ;  mark 
with  a  scribe  on  the  piston-rod  at  the  face  of  the  stuffing-box 
follower  on  steam  end  ;  then  move  the  piston  to  its  contact  stroke 
on  the  opposite  end  and  make  another  mark  on  the  piston-rod, 
exactly  half  way  between  the  face  of  the  stuffing-box  follower  on 
the  steam  end,  and  the  first  mark.  Then  move  the  piston  back 
until  the  middle  mark  is  at  the  face  of  piston-rod  stuffing-box 
follower  on  the  pump  end.  This  operation  brings  the  piston 
exactly  in  the  middle  of  the  stroke.  Then  take  off  the  steam 


HANDBOOK    ON    ENGINEERING.  f)69 

chest  cover,  place  the  slide-valve  in  the  center,  exactly  over  the 
steam  ports.  Place  the  slide-valve  nut  in  exact  center  between 
the  jaws  of  the  slide-valve,  screw  the  valve-rod  through  the  nut 
until  the  eye  on  the  valve-rod  head  comes  in  line  with  the  eye  of 
the  valve-rod  link  ;  slip  the  valve-rod  head  pin  through  head  and 
the  valve  is  set.  Repeat  the  same  operation  on  the  other  side  of 
the  pump.  Where  a  pump  is  fitted  with  four  hexagon  valve-rod 
nuts,  two  either  end  of  the  slide-valve,  instead  of  one  nut  in  the 
center  of  the  valve,  set  and  lock  these  hexagon  nuts  at  equal  dis- 
tances from  the  outer  end  of  the  slide-valve  jaws,  allowing  a  little 
lost  motion,  varying  from  J"  on  high-pressure  pumps,  to,  say, 
J"  on  low  service  pumps,  on  each  side  of  valve ;  if  the  steam 
piston  hits  the  head,  take  up  some  of  your  lost  motion ;  if  the 
steam  piston  should  not  make  a  full  stroke,  give  more  lost  motion. 

THE  BEST  MANNER  OF  ARRANGING  PIPE  CONNECTIONS. 

For  the  purpose  of  showing  good  arrangement,  the  following 
cut  is  presented. 

On  long  lifts  it  is  necessary  to  provide  the  suction  pipe  S 
with  a  foot-valve  F.  By  the  use  of  a  foot-valve,  the  pipe  and 
cylinders  are  constantly  kept  charged  with  water,  allowing  the 
pump  to  start  without  having  to  free  itself  and  the  suction  pipe 
of  air.  In  case  of  a  long  lift,  the  vacuum  chamber  V  is  also 
essential.  This  may  be  readily  constructed  by  using  a  tee  in  place 
of  the  elbow  E,  extending  the  suction  pipe  and  placing  a  cap 
upon  the  top.  In  order  to  keep  the  water  back  when  the  pump  is 
being  examined  or  repaired,  a  gate  valve  should  be  placed  in  the 
delivery  pipe.  It  sometimes  happens  that,  either  purposely  or 
through  a  leak  in  the  foot-valve,  the  suction  chamber  becomes 
empty.  For  the  purpose  of  charging  the  suction  pipe  and  cylin- 
der a  "  charging  pipe  "  P  is  placed  outside  the  check  valve, 
connecting  the  delivery  pipe  D  with  the  suction.  In  order  that 


570 


HANDBOOK    ON    EX(!  INHERING. 


the  pump,  in  starting,  may  free  itself  of  air,  a  check  valve  (7  and 
a   "  starting    pipe"  A  should    be  provided.     This  pipe  may  be 


ARRANGEMENT  OF  PIPE  CONNECTIONS. 


led  to  any  convenient  place  of  discharge.  After  the  pump  has 
started,  the  valve  in  the  starting  pipe  should  be  closed  gradually. 
Faulty  connections  are  generally  the  cause  of  the  improper  action 


HANDBOOK    ON    ENGINEERING.  571 

of  a  pump.  Great  care  should,  therefore,  be  taken  to  have 
everything  right  before  starting.  A  very  small  leak  in  the  suc- 
tion will  cause  a  pump  to  work  badly. 

Q.  What  is  the  peculiarity  of  the  duplex  type?  A.  There  are 
two  steam  cylinders  and  two  water  cylinders ;  the  piston  of  one  of 
these  cylinders  works  the  valve  of  the  other  cylinder,  and  vice  versa. 
Neither  half  can  work  alone.  This  name  is  entirely  arbitrary. 

Q.  How  would  you  call  a  pumping  machine  in  which  there  are 
two  steam  cylinders,  each  operating  a  water  cylinder  in  line  with 
it ;  each  half  being  a  perfect  pumping  machine  independent  of  the 
other  side?  A.  A  "  double  "  pump. 

Q.  Can  a  direct  acting  steam  pump  use  steam  expansively? 
A.  Not  to  any  extent ;  in  fact,  there  would  be  danger  of  sticking 
upon  the  centers  in  most  cases,  if  there  was  lap  and  expansion. 

Q.  What  is  the  reason  that  a  single  cylinder  engine  cannot  well 
reverse  itself  without  a  fly  wheel,  by  means  of  the  ordinary  single 
D  valve?  A.  Because  when  the  valve  was  at  mid-travel,  both 
ports  of  the  valve  seat  would  be  closed  by  the  valva  faces,  and 
neither  exhaust  nor  admission  take  place. 

Q.  What  means  are  employed  in  a  direct  acting  steam  pump  to 
move  the  valve?  A.  A  small  supplementary  piston  is  used;  this 
supplementary  piston  being  actuated  by  the  main  piston  in  any 
one  of  several  different  ways. 

Q.  What  are  the  principal  ways  of  working  the  supplementary 
piston  from  the  main  piston?  ,A.  (1)  The  main  piston  strikes 
the  tappet  of  a  small  valve,  which  opens  an  exhaust  passage  in 
one  end  of  the  cylinder,  containing  a  supplementary  piston,  and 
having  live  steam  pressing  upon  both  ends  of  the  supplementary 
piston  ;  (2)  by  the  main  piston  striking  a  rod  passing  through 
the  cylinder  head,  and  moving  a  lever  which  controls  the  motion 
of  the  part  of  the  main  valve  to  which  is  attached  the  valves  which 
moves  the  supplementary  piston  ;  (3)  the  main  piston  rod  carries 
a  tappet  arm,  which  twists  the  stem  of  the  supplementary  piston, 


572  HANDBOOK    ON    ENGINEERING. 

thus  uncovering  ports  which  cause  its  motion ;  (4)  a  projection 
upon  the  main  piston  rod  engages  the  stem  and  operates  the  valve 
which  moves  the  supplementary  piston,  but  if  that  valve  should 
not,  by  means  of  its  steam  passages,  cause  quick  enough  or  sure 
enough  motion  of  the  supplementary  piston,  a  lug  upon  this  stem 
moves  the  supplementary  piston. 

Q.  In  the  first  of  these  four  classes,  what  is  the  principal 
element  in  the  valve  motion?  A.  A  difference  in  area  between 
the  eduction  port  of  the  supplemental  piston  and  its  induction  port 

Q.  What  is  the  principal  feature  in  the  second  class?  A.  A 
regular  slide  valve  letting  steam  upon  alternate  ends  of  the  sup- 
plemental piston. 

Q.  In  the  third  class,  what  is  the  main  feature?  A.  A  twist- 
ing motion  in  the  supplemental  piston. 

Q.  In  the  fourth  class,  what  is  the  principal  feature?  A. 
Movement  of  the  supplemental  piston  by  steam  controlled  by  a 
slide  valve,  and  by  the  mechanical  action  of  the  slide  valve  itself 
if  its  steam  distribution  is  defective. 

Q.  .What  are  the  objections  to  most  pumps  of  the  direct  acting 
type?  A.  The  unbalanced  condition  of  the  auxiliary  pistons  in 
the  exhaust  side,  causing  a  loss  of  steam  when  the  parts  are  worn, 
the  choking  up  of  the  small  ports  for  the  auxiliary  pistons,  by  the 
gumming  and  caking  of  the  oil  therein. 

Q.  Can  the  ordinary  direct  acting  steam  pump  use  steam 
expansively?  A.  No. 

Q.   How  may  this  be  done?     A.  By  compounding. 

Q.  What  is  to  be  taken  into  consideration  in  the  use  of  com- 
pound steam  pumps?  A.  That  they  are  designed  for  a  certain 
range  of  pressure  —  say  from  80  to  120  pounds  boiler  pressure, 
and  will  do  their  best  work  between  these  pressures. 

Q.  Have  all  direct-acting  steam  pumps  intermittent  valve 
motion?  A,  No;  there  are  some  which  have  continuous  valve 
motion, 


HANDBOOK    ON    ENGINEERING.  573 

Q.  In  most  direct-acting  steam  pumps,  are  the  auxiliary  piston 
heads  made  together  or  in  separate  pieces?  A.  Together. 

Q.  They  are  in  contact  with  the  steam  in  the  chest?     A.  Yes. 

Q.  What  should  be  said  about  the  location  of  a  pump?  A.  It 
should  be  as  near  the  source  of  supply  as  is  convenient. 

Q.  What  may  be  said  about  convenience  in  repairs?  A.  The 
pump  should  have  room  left  upon  all  sides ;  and  upon  both  ends 
equal  to  its  length,  for  the  removal  of  the  piston  rods  in  case  of 
repairs. 

Q.  If  the  floor  is  not  strong  enough,  how  may  a  good  founda- 
tion be  made  ?  A.  By  digging  two  or  three  feet  into  the  ground 
and  building  up  the  proper  height  with  stone  or  brick  laid  in 
strong  cement,  with  a  cap  stone. 

Q.  What  may  be  said  about  suction  pipes?  A.  They  must  be 
as  large  as  possible ;  the  longer  they  are  the  greater  in  diameter 
they  should  be ;  they  should  be  as  straight  as  possible,  and  as 
free  from  bends  and  valves  ;  they  must  be  air-tight ;  they  must 
not  be  allowed  to  get  obstructed  by  foreign  substances. 

Q.  What  may  be  said  about  the  area  of  strainer  holes?  A. 
They  should  have  an  aggregate  area  about  live  times  that  of  the 
suction  pipe. 

Q.  Where  are  foot  valves  necessary  ?  A.  Upon  long  suctions 
or  high  lifts. 

Q.  Should  two  pumps  take  their  suction  from  one  pipe  ?  A.  It 
should  be  avoided,  unless  the  pipe  is  very  large  ;  and  in  case  both 
suctions  should  be  arranged  so  that  one  of  the  pumps  should  not 
have  to  draft  at  right-angles  to  the  flow  of  water  going  to  the  other 
pump. 

Q.  What  arrangement  should  be  made  where  it  is  necessary  to 
have  two  pumps  draft  from  one  Suction  ?  A.  There  should  be  a 
Y  connection. 

Q.  What  is  a  good  way  to  reduce  the  friction  in  suction  pipes 
where  tfrere  are  many  bends?  A.  To  use  bends  of  wrought- 


574  HANDBOOK    ON    ENGINEERING. 

iron  pipe  of  as  long  a  radius  as  possibler  instead  of  cast-iron 
elbows. 

Q.  What  may  be  said  about  the  lower  end  of  the  suction  pipe? 
A.  It  should  generally  have  a  strainer ;  and  if  the  lift  is  over  12 
to  15  feet,  should  have  a  foot  valve. 

Q.  What  is  a  good  thing  to  do  witli  the  discharge  pipe  near 
the  pump?  A.  To  put  a  valve  in  it  near  the  pump,  to  keep 
the  water  in  the  pipe  when  the  water  end  is  to  be  opened  for 
inspection  or  repairs. 

Q.  What  provision  should  be  made  for  priming  the  pump?  A. 
There  should  be  a  pipe  with  a  stop  valve  in  it  connected  from  the 
discharge  pipe  beyond  this  check  valve,  or  from  some  other  source 
of  supply,  to  the  suction  pipe,  for  the  purpose  of  priming  the 
pump. 

Q.  When  the  pump  is  in  position  for  piping,  what  care  should 
be  taken?  A.  That  the  pipes  are  of  proper  length,  so  as  not  to 
bring  any  undue  strain  upon  them  in  connecting  them  to  the  pump, 
as  in  that  case  they  will  be  liable  to  give  trouble  by  breaking  or 
working  the  joints  loose  and  leaking. 

Q.  Does  any  pipe  have  an  effective  diameter  as  great  as  its 
nominal  diameter?  A.  No;  because  the  sides  retard  the  flow  of 
the  liquid ;  there  is  a  neutral  film  of  liquid  which  practically  does 
not  move. 

Q.  Upon  what  does  the  thickness  of  this  lilmof  liquid  depend  ? 
A.  Upon  the  viscosity  (commonly  miscalled  the  "  thickness  ") 
of  the  liquid ;  upon  the  roughness,  material  and  diameter  of  the 
pipe  ;  the  pressure,  etc. 

Q.  When  long  lines  of  pipe  are  used,  should  the  diameter  of  the 
pipe  be  the  same  all  the  way  along,  or  should  there  by  sections 
be  decreasing  diameter,  as  the  distance  from  the  pump  increases? 
A.  Most  emphatically,  the  pipe  diameter  should  remain  constant 
clear  out  to  the  end. 


HANDBOOK    ON    ENGINKKKING.  575 

TAKING  CARE  OF  A  PUMP. 

Q.  What  can  be  said  about  taking  care  of  a  pump?  A.  In 
places  where  an  inferior  grade  of  labor  is  employed,  oil  and  dirt 
are  sometimes  found  covering  the  steam  chest  and  pump  to  the 
depth  of  an  inch  in  thickness ;  stuffing  boxes  are  allowed  to  go 
leaky  and  get  loose ;  the  valve  motion  is  never  looked  after ;  lost 
motion  is  never  taken  up,  and  the  pump  will  be  let  run  in  a  slip- 
shod way  for  months,  until  some  accident  occurs.  This  will 
sometimes  exist  in  places  where  the  engine  is  well  taken  care  of. 

Q.  Should  not  as  good  care  be  taken  of  a  steam  pump  as  of 
an  engine?  A.  Yes.  It  is  a  steam  engine,  and  the  fact  that  it 
has  generally  but  little  adjustability,  should  not  render  it  liable  to 
lack  of  care. 

Q.  What  is  a  very  common  thing  for  pump  runners  to  do  when 
anything  happens?  A.  To  condemn  the  pump  at  once  without 
finding  out  the  cause  of  the  trouble. 

Q.  What  is  one  reason  of  this?  A.  The  man  who  understands 
an  ordinary  engine,  will  often  become  quite  perplexed  when  he 
examines  the  steam  end  of  a  direct  acting  steam  pump,  because 
he  does  not  comprehend  the  principal  feature  of  its  construc- 
tion—  that  all  direct  acting  steam  pumps  which  have  no  fly 
wheels  and  cranks,  must  generally  have  an  auxiliary  piston  in 
order  to  carry  them  over  the  "dead  center."  A  direct  acting 
steam  pump  is  really  a  double  engine;  a  plain,  flat  slide,  valve 
admitting  steam  to  a  small  piston,  which  in  turn  operates  the 
main  valve,  which  gives  steam  by  the  usual  arrangement  to  the 
main  piston. 

Q.  What  would  save  firemen  and  engineers  much  trouble  with 
steam  pumps?  A.  If  they  would  take  the  trouble  to  examine 
their  pumps  carefully,  and  find  out  the  way  their  valves  were 
arranged  and  actuated. 

Q.  Upon    what  does  the    successful  performance    of    a  pump 


576  HANDBOOK    ON    KNiilNKKRTNG. 

depend,  in  great  measure?  A.  Upon  its  proper  selection  from 
among  the  many  patterns  differing  from  each  other  in  size,  pro- 
portion and  general  arrangement. 

Q.  What  may  be  said  about  the  selection  of  pumps?  A. 
Pumps  are  often  selected  improperly  for  their  work.  As  an  illus- 
tration, a  man  who  wishes  to  use  a  circulating  pump  for  a  surface 
condenser,  where  the  water  pressure  upon  the  pump  cylinder  will 
never  exceed  5  to  10  pounds,  will  buy  a  pump  intended  for  boiler 
feed  work,  and  having  its  steam  cylinder  about  three  times  the 
area  of  its  pump  cylinder. 

Q.  What  will  be  the  result  in  such  a  case?  A.  There  will  be 
little  or  no  pressure  in  the  steam  cylinder  when  working  on  the 
condenser ;  and  while  there  is  pressure  sufficient  to  move  the 
main  piston,  there  is  not  enough  to  operate  the  auxiliary  piston 
with  positiveness. 

Q.  In  ordering  a  pump,  or  in  asking  estimates,  what  informa- 
tion should  be  given?  A.  In  ordering  a  pump,  it  is  to  the  inter- 
est of  the  purchaser  to  fully  inform  the  maker  or  seller  on  the 
following  questions :  1st.  For  what  purpose  is  the  pump  to  be 
used?  What  is  the  average  steam  pressure?  2d.  What  is  the 
liquid  to  be  pumped  ;  and  is  it  hot  or  cold,  clear  or  gritty,  fresh, 
salt,  alkaline  or  acidulous?  3d.  What  is  the  maximum  quantity 
to  be  pumped  per  minute  or  hour?  4th.  To  what  height  is  the 
liquid  to  be  lifted  by  suction,  and  what  is  the  length  of  the  suction 
pipe,  and  the  number  of  elbows  or  bends?  5th.  To  what  height 
is  the  liquid  to  be  pumped,  and  what  is  the  length  of  discharge 
pipe? 

Q.  How  can  an  engineer  familiarize  himself  with  the  direction 
of  the  auxiliary  steam  and  exhaust  passages?  A.  By  means  of 
a  piece  of  wire. 

Q.  What  is  the  special  thing  to  look  after  in  duplex  pumps? 
A.  That  all  packings  are  adjusted  uniformly  on  both  sides. 

Q.  What  would  be  the  result  of  having  the  packings  different 


HANDBOOK    OX    ENGINEERING.  577 

i>pon  the  two  sides  of  a  duplex  pump?  A.  The  machinery  would 
run  unsteadily. 

(J.  If  :i  pump  works  badly,  what  should  be  about  the  first  thing 
to  look  at?  A.  The  connections. 

Q.  When  a  pump  is  first  connected,  what  should  be  done? 
A.  It  should  be  blown  through  to  remove  dirt ;  if  it  be  of  the 
class  which  will  permit  of  removing  the  bonnets  and  blowing 
through,  that  should  be  done. 

Q.  What  pump  piston  speed  is  recommended  for  continuous 
boiler  feeding  service?  A.  About  50  feet  per  minute. 

Q.  What  may  be  said  about  the  care  and  use  of  steam  pumps 
of  all  kinds?  A.  It  is  important  that  the  pump  be  properly  and 
thoroughly  lubricated  ;  that  all  stulling-box,  piston  and  plunger 
packings  be  nicely  adjusted  ;  not  so  tight  as  to  cause  undue  fric- 
tion ;  nor  so  slack  as  to  leak  badly. 

Q.  In  which  end  of  a  steam-pumping  machine  is  there  most 
likely  to  be  trouble?  A.  In  the  water  end. 

Q.  If  a  pump  slams  and  hammers  in  its  water  end,  is  it  neces- 
sarily defective  in  its  water  cylinder?  A.  No;  it  may  be  that 
there  is  no  suction  chamber,  or  not  enough  ;  or  sometimes  it  slams 
because  the  suction  pipe  is  not  large  enough. 

Q.  What  are  very  common  defects  in  cheap  grades  of  pumps  i 
A.  Too  little  valve  area  in  the  pump  end;  too  great  lift  for  the 
valves. 

Q.  What  are  the  principal  causes  of  pumps  refusing  to  lift 
water  from  the  source  of  supply?  A.  Among  these  majr  be 
mentioned  leaky  suction  pipes,  worn  out  pistons,  plungers,  pack- 
ings or  water  valves ;  rotten  gaskets  on  joints  in  piping  or  pump ; 
and  sometimes  a  failure  to  properly  prime  the  pump  as  well  as 
the  suction  pipe. 

Q.  What  is  one  great  cause  of  a  pump  refusing  to  lift  water 
when  lirst  started?  A.  It  often  happens  that  a  pump  refuses  to 
lift  water  while  the  full  pressure  against  which  it  is  expected  to 

37 


578  HANDBOOK    ON    ENGINEERING. 

work  is  resting  upon  the  discharge  valves,  for  the  reason  that  the 
air  within  the  pump  chamber  is  not  dislodged,  but  only  compressed, 
by  the  motion  of  the  plunger.  It  is  well,  therefore,  to  arrange 
for  running  without  pressure  until  the  air  is  expelled  and  water 
follows ;  this  is  done  by  placing  a  valve  in  the  delivery  pipe 
and  providing  a  waste  delivery,  to  be  closed  after  the  pump  has 
caught  water. 

Q.  Sometimes  when  starting,  the  water  may  not  come  for  a 
long  time  ;  what  is  the  best  thing  to  do  in  this  case?  A.  First, 
open  the  little  air  cock,  which  is  generally  located  in  the  top  of 
the  pump,  between  the  discharge  valves  and  the  air  chamber,  to 
let  off  any  accumulation  of  air  which  may  there  be  confined 
under  pressure.  Very  often,  by  relieving  the  pump  of  this  air 
pressure,  it  will  pick  up  its  water  by  suction  and  operate 
promptly. 

Q.  What  precaution  must  be  taken  in  priming  the  pump?  A. 
The  air  cock,  which  should  be  provided  at  the  top  of  the  pump, 
should  be  opened  to  allow  the  escape  of  the  air  from  the  suction 
pipe  and  from  the  pump,  and  then  the  valve  in  the  priming  pipe 
should  be  opened.  The  pump  should  then  be  started  slowly,  as 
it  aids  in  more  completely  filling  the  pump  cylinders,  which 
otherwise,  might  not  occur  and  the  pump  might  fail  to  lift  water. 

Q.  Is  there  any  advantage  in  having  air  in  the  suction?  A. 
Sometimes  a  small  amount  of  air  let  into  the  suction  will  cause  less 
jarring  when  the  duty  is  very  heavy. 

Q.  What  may  be  said  about  pumping  hot  water?  A.  Where 
the  hot  water  is  very  hot,  it  should  gravitate  to  the  pump,  instead 
of  an  attempt  being  made  to  draft  it. 

Q.  In  the  plunger  pumps,  what  is  about  the  only  wearing  part 
of  the  water  end?  A.  The  packing  of  the  plunger  stuffing-boxes. 

Q.  How  can  a  pump  be  prevented  from  freezing?  A.  By 
having  draining  cocks  and  opening  them  when  the  pump  is 
idle. 


HANDBOOK    ON    ENGINEERING. 

Q.  What  may  be  said  about  leather  piston  packing  for  water 
cylinders?  A.  For  cold  water,  or  sandy,  gritty  water,  the 
leather  packing  has  many  points  to  commend  it ;  it  makes  a 
tight  piston,  and  one  that  is  the  least  destructive  to  pump 
cylinders. 

Q.  What  is  the  best  way  to  handle  the  square  packing  mostly 
employed,  which  is  composed  of  alternate  layers  of  cotton  and 
rubber?  A.  Cut  the  lengths  a  trifle  short,  then  there  will  be 
room  for  the  packing  to  swell  and  not  cause  too  much  friction.  I 
have  known  pistons  where  this  precaution  has  not  been  taken  to 
be  fastened  so  securely  in  the  cylinder  by  the  swelling  of  the  dry 
packing,  that  full  steam  pressure  could  not  move  them. 

Q.  What  is  the  remedy  in  such  a  case?  A.  Remove  the 
follower,  take  out  the  different  layers  of  packing  and  shorten  their 
lengths. 

Q.  What  is  the  reason  that  some  soft  waters  corrode  pipes  so 
often?  A.  Because  they  contain  a  large  proportion  of  oxygen. 

Q.  Will  a  pump  with  a  6"  water  cylinder  and  a  6"  steam  cylin- 
der force  water  into  a  boiler,  the  discharge  from  water  cylinder 
being  4"  diameter;  boiler  pressure,  80  Ibs.?  A.  A  pump  with  a 
6"  water  cylinder  and  6"  steam  cylinder  will  not  force  water  into 
the  boiler  which  supplies  it,  no  matter  what  the  steam  pressure, 
nor  what  the  size  of  discharge  pipe.  It  will  not  move.  The 
pressures  would  be  equalized  and  there  would  be  nothing  to  over- 
come friction  of  steam  and  water  in  pipes  and  cylinder.  The 
foregoing  case  supposes  that  the  water  is  to  be  lifted  to  the  pump  ; 
or  at  least  that  there  shall  be  no  head ;  also,  that  there  shall  be 
no  fall  from  pump  to  boiler.  If  there  were  sufficient  head  or  fall 
to  overcome  all  the  various  frictions,  and  no  lift,  the  pump 
would  apparently  work ;  but  really,  the  water  piston  would  be 
dragging  the  steam  piston  along. 

Q.  How  may  acids  be  pumped?  A.  By  what  is  known  as 
blowing  up ;  that  is,  by  employing  a  pump  to  put  pressure  upon 


580  HANDBOOK    OX     KNCIINKKKI  N(J . 

the  acid  in  a  closed  vessel,  thereby  forcing  it  through  a  pipe 
placed  in  the  bottom  of  the  vessel. 

Q.  .In  case  any  wearing  part  of  :i  pump  gets  to  cutting,  what 
should  be  done?  A.  If  it  is  not  practicable  to  stop  the  pump  nor 
to  reduce  its  speed,  the  part  which  is  getting  damaged  should  be 
given  very  liberal  oiling. 

Q.  What  is  the  best  oil  for  this  purpose?  A.  That  depends  on 
the  nature  of  the  cutting  surfaces,  and  on  the  pressure  therein : 
the  mineral  oils  are  generally  more  cooling  than  others,  although 
they  have  .less  body  to  resist  squeezing. 

CALCULATING  THE  BOILER  FOR  A  STEAM  PUMP. 

The  amount  of  work  which  a  boiler  has  to  do  is  very  easy  of 
determination.  Given  the  largest  number  of  gallons  which  a 
pump  will  be  required  to  pump  per  minute,  and  the  height  in  feet 
from  the  surface  of  the  well  from  which  the  water  is  drawn,  to 
the  point  of  discharge,  you  can  easily  tell  by  multiplying  by  8J — 
the  weight  in  pounds  of  one  gallon  —  the  number  of  foot  pounds 
of  power  consumed  per  minute  in  lifting  the  water,  adding  a  cer- 
tain percentage  for  friction  of  the  machine  and  of  water  in  the 
pipe,  we  have  the  total  number  of  foot  pounds  consumed  per 
minute,  and  this  divided  by  33,000  will  be  the  horse  power 
consumed . 

The  allowance  for  friction  will  vary  with  the  style,  size  and 
condition  of  the  pump,  the  size  of  the  pipe,  and,  above  all,  the 
manner  in  which  the  pipe  is  connected  up,  the  number  of  right 
angle  turns,  etc. 

This  may  be  arrived  at  in  another  way.  A  column  of  water 
2.o  feet  in  height  exerts  a  pressure  of  one  pound.  Allowing  the 
.3  for  friction,  we  can,  by  dividing  the  total  left  in  feet  by  two, 
get  at  the  pressure  per  square  inch,  which  is  being  exerted  against 
the  water  piston  or  plunger,  and  multiplying  by  the  number  of 


HANDBOOK    ON    ENGINEERING.  581 

square  inches  in  that  piston  gives  the  total  pressure  against  which 
the  pump  is  working.  This  multiplied  by  the  piston  speed  in  feet 
minutes,  and  divided  by  33,000,  will  give  the  lift  in  horse  power. 
In  this  case,  as  in  the  other,  the  lift  must  be  calculated  from  the 
surface  of  the  supply,  and  not  from  the  pump,  when  the  pump  is 
lifting  its  supply.  If  the  water  flows  to  the  pump  it  must  be 
calculated  from  the  height  of  the  water  cylinder.  An  allowance 
of,  say,  25  per  cent,  should  be  made  above  the  horse  power  thus 
shown,  in  order  to  provide  for  contingencies,  and  to  be  on  the 
safe  side. 

In  selecting  &  boiler  to  do  this  work,  it  must  be  borne  in  mind 
that  a  boiler  which  is  sold  for  a  certain  horse  power,  is  supposed 
to  be  able  to  furnish  that  power  in  connection  with  a  good  steam 
engine ,  and  they  are  not  apt  to  be  overrated .  Now ,  the  steam  pu m  p 
as  usually  built,  does  not  approach  in  economy  the  ordinary  steam 
engine,  and,  therefore,  a  boiler  which  will  develop  twenty-five 
horse  power  in  connection  with  a  good  engine  would  be  too  small 
for  a  pump  which  was  required  to  do  the  same  amount  of  work. 
The  evaporation  of  30  pounds  of  water  per  hour  from  feed  at  100 
degrees  Fahr.  into  steam  of  70  Ibs.  pressure,  has'been  adopted  by 
several  authorities  as  a  horse  power.  Any  good  automatic  cut-off 
will  run  on  this  amount  of  water,  and  if  an  estimate  can  be  made 
of  the  comparative  performance  of  the  pump  under  consideration, 
a  close  approximation  to  the  desired  size  of  boiler  can  be  made. 

THE  WORTHINQTON  WATER  METER. 

The  counter  registers  cubic  feet;  one  foot  being  7  T4^  gallons, 
United  States  standard.  It  is  read  in  the  same  way  as  registers 
of  gas  meters.  The  following  example  and  directions  may  be  of 
use  to  those  unacquainted  with  the  method :  If  a  pointer  is 
between  two  figures,  the  smaller  one  must  invariably  be  taken. 
Suppose  the  pointers  of  the  dials  to  stand  as  in  the  engraving. 


582 


HANDBOOK    ON    ENGINEERING. 


The  reading  is  6,874  cubic  feet.  From  the  dial  marked  ten  w- 
get  the  figure  4  ;  from  the  next,  marked  hundred,  the  figure  7  ; 
from  the  next,  marked  thousand,  the  figure  8  ;  from  the  next, 


marked  ten  thousand,  the  figure  6.  The  next  pointer  being 
between  ten  and  1,  indicates  nothing.  By  subtracting  the  read- 
ing taken  at  one  time,  from  that  taken  at  the  next,  the  consump- 
tion of  water  for  the  intermediate  time  is  obtained. 


TABLE    OF    PRESSURE    DUE    TO    HEIGHT. 


ressure 
nch. 

ressure 
nch. 

1 

£•§ 

2  a 

ressure 
nch. 

£  fl 

3   . 

ll 

^ 

ft'"] 

Is 

ft  . 

ii 

ft": 

*i 

ft  . 

| 

ft'" 

i 

^"t 

| 

ft"! 

05 

O5     5T 

0 

OJ     M 

a? 

OJ    S'        '      ® 

Ml    «J 

1C     C/l 

9 

«>    W 

O5    OD 

"3  si 

oJ   '-> 

i  5 

•3  ^ 

c3   Vi 

•^ 

*3  t. 

—  ' 

-3  ^ 

•* 

03    - 

« 

&  ft 

a? 

&ft 

!    0) 

S.& 

OJ 

CTft 

cu 

0) 

&& 

g 

S-^ 

i 

P    y 

cr  ft 

fc 

w 

fe 

H 

I  SH 

H 

M 

H 

H 

a 

1 

0.43 

15 

6.49 

30 

12.99 

45 

19.49 

60 

25  99 

75 

32.48 

90 

38.98 

5 

2.16 

20 

8  66 

35 

15  16 

50 

21.65 

65 

28  15 

80 

34  65 

95 

41  15 

10 

4  33 

25 

10.82 

40 

17.32 

55 

23.82 

70 

30  32 

85 

36.82 

100 

48  31 

HANDBOOK    ON    ENGINEERING. 


583 


TABLE  OF  DECIMAL   EQUIVALENTS  OF  8ths,  16ths, 
32ds  AND  64ths  OF  AN  INCH. 


8ths. 


32ds. 


64ths. 


64ths. 


1 

— 

.125            r/2 

— 

.03125     -6L4- 

-H 

.015625     ||  = 

.546875 

1 

= 

.25       -3\ 

= 

.09375 

a; 

.046875 

.578125 

i 



.375      36,- 

.50          ,& 

= 

.15625 
.21875 

| 

= 

.078125     ||  = 
.109375 

.609375 
.640625 

1 

BD 

.625 

& 

= 

.28125 

f\ 

r= 

.140625 

.671875 

1 



.75 

= 

.34375 

(Td 



.171875 

AJ 

-  — 

.703125 

1 

—  . 

.875 

H 

3s 



.40625 

-_ 

.203125     H 

.  -—  . 

.734375 

ft 

— 

.46875 

— 

.234375 

\ 



.765625 

= 

.53125 

=1= 

.265625 

\ 

= 

.796875 

I6ths. 

32 

= 

.59375     L» 

rr= 

.296875 

I 

•  = 

.828125 

I* 



.65625 

64 



.328125 

s 

.  __ 

.859375 

uf 

= 

.0625 



.71875 

•|| 

33- 

.359375 

1; 

•  

.890625 

A 

= 

1875 

= 

.78125     |f 

s 

.390625 

64  ^ 

.921875 

I 

= 

.3125 

= 

.84375 

H 

= 

.421875 

64  == 

.953125 



.4375 



.90625 

H 

—  - 

.453125 

.984375 

A 

— 

.5625 

— 

.96875 

31 
6  4 



.484375 

1L 

= 

.6875 

II 

6  4 

—  - 

.515625 

16 



.8125 

tj 

= 

.9375 

LATENT   HEAT   OF   LIQUIDS,    UNDER   A   PRESSURE 
OF  SO  INCHES  OF  MERCURY. 

(TREATISE    OX    HEAT,    BY    THOMAS    BOX.) 


Latent  Heat 
in  Units. 

Increase  of  Tempe- 
rature of  Liquid, 
if  Heat  bad  not 
become  Latent. 

Water  

966 

966° 

Regnault 

457 

735° 

Ure 

Ether  

313 

473° 

a 

Oil  of  Turpentine.  .  .  
Ntiphthti  .      . 

184 

184 

390° 

443° 

«< 
tt 

The  Boiling  Point  of  different  Liquids  varies;  and  the  Boiling  Point 
of  a  liquid  varies  with  the  pressure. 


584 


HANDBOOK    ON    ENGINEERING. 


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HANDBOOK    ON    ENGINEERING. 


585 


CAPACITY  OF  SQUARE   CISTERNS  IN  U.  S.  GALS. 


5X5 

5X« 

5X7 

5X8 

5X9  5X10 

6X6 

6X7 

6X8 

6X9 

6X10 

5  ft..   935 

1122 

1309 

1496  1683  1870 

1346 

1571 

1795 

2020 

2244 

54ft..  1028 

1234 

1440 

1645 

1851 

2057 

1481 

1728 

1975 

2221 

2469 

G  ft..  1122 

1346 

1571 

1795 

2019 

2244 

1615 

1885 

2154 

2423 

2693 

(54  ft.-  1215 

1459 

1702 

19*5 

2188 

2431 

1750 

2042 

2334 

2625 

2917 

7  ft..  1309 

1571 

1833 

2094 

2356 

2618 

1884 

2199 

2513 

2827 

3142 

74  ft..  1403 

1683 

1963 

2244 

2524 

2800 

2019 

2356 

269313029 

3366 

H  ft..  1496 

1795 

2094 

2393 

2693 

2992 

2154 

2513 

2872 

3231 

3592 

S4ft..  1589 

1907 

2225 

2543 

2861 

3179 

2288 

2670 

3052 

3433 

3816 

'.)  ft.. 

1683 

2020 

2356 

2693 

3029 

3366 

2423 

2827 

3231 

3635 

4041 

94ft.. 

1776 

2132 

2487 

2842 

3197 

3553 

2558 

2984 

3412 

3837 

4265 

10  ft..  1870 

2244 

2618 

2992 

3366 

3470 

2692 

3142  3591 

4039 

4489 

1 

«XH  6X1217X77X8 

7X9 

7X10 

7XH 

7X12 

8X8 

8X9 

5  ft.. 

24G8   2693 

1832  2094 

2356 

2618 

2880 

3142 

2394 

2693 

54  ft.  . 

2715   2962 

20162304 

2592 

2880 

3168 

3456 

2633 

2962 

<;  ft.. 

2962   3231 

21992513 

2827 

3142 

3456 

3770 

2872 

3231 

64  ft.. 

3209   3500 

2382'2722 

3063 

3403 

3744 

4084 

3112 

3500 

7  ft.. 

3455   3770 

25652932 

3298 

3665 

4032 

4398 

3351 

3770 

74ft.. 

3702   4039 

27483141 

3534 

3927 

4320 

4712 

3590 

4039 

8  ft.. 

3949   4308 

2932'3351 

3770 

4189 

4608 

5026 

3830 

4308 

84ft.. 

4196  :  4577 

31153560 

4005 

4451 

4896 

5340 

4069 

4578 

y  ft.. 

4443   4847  329813769 

4341 

4712 

5184 

5655 

4308 

4847 

94  ft.. 

4689   5116  3481,3979 

4576 

4974 

5472 

5969 

4548 

5116 

10  ft.. 

4936   5386 

3664  4188 

4712 

5236 

5760 

6283 

4788 

5386 

WEIGHT    OF    WATER. 


1  cubic  inch 

12  cubic   inches 

1  cubic  foot  (salt)  . . 
1  cubic  foot  (fresh) 
1  cubic  foot 


.03617  pound. 

.434      pound. 
64. 3  pounds. 

62.425      pounds. 
7.48         U.  S.  Gallons. 


NOTE.  —  The  center  of  pressure  of  a  body  of  water  is  at  two-thirds 
the  depth  from  the  surface 

To  find  the  pressure  in  pounds  per  square  inch  of  a  column  of  water, 
multiply  the  height  of  the  column  in  feet  by  .434.  Every  foot  elevation 
is  called  (approximately)  equal  to  onS-half  pound  pressure  per  square 
inch. 


586 


HANDBOOK    ON    ENGINEERING. 


SHOWING    U.    S.    GALLONS   IN    GIVEN 
CUBIC   FEET. 


NUMBER   OF 


Cubic 

Feet. 

Gallons. 

Cubic 
Feet. 

Gallons. 

Cubic  Feet. 

Gallons. 

0.1 

0.75 

50 

374.0 

9,000              67,324.6 

0.2 

1.50 

60 

448.8 

10,000              74,805.2 

0.3 

2.24 

70 

523.6 

20,000            149,610.4 

0.4 

2.99 

80 

598.4 

30,000            224,415.6 

0.5 

3.74 

90 

673.2 

40,000            299,220.7 

0.6 

4.49 

100 

748.0 

50,000            374,025.9 

0.7 

5.24 

200 

1,496.1 

60,000 

448,831.1 

0.8 

5.98 

300 

2,244.1 

70,000 

523,636.3 

0.9 

6.73 

400 

2,992.2 

80,000 

598,441.5 

1 

7.48 

500 

3,740.2 

90,000 

673,246.7 

2 

14.9 

600 

4,488.3 

100,000 

748,051.9 

3 

22.4 

700 

5,236.3 

200,000 

1,496,103.8 

4 

29.9 

'      800 

5,984.4 

300,000 

2,244,155.7 

5 

37.4 

900 

6,732.4 

400,000 

2,992,207.6 

6 

44.9 

1,000 

7,480.0 

500,000 

3,740,259.5 

7 

52.4 

2,000 

14,961.0 

600,000 

4,488,311.4 

8 

59.8 

3,000 

22,441.5 

700,000 

5,236  363.3 

9 

67.3 

4,000 

29,922.0 

800,000 

5,984,415.2 

10 

74.8 

5,000 

'  37,402.6 

900,000 

6,732,467.1 

20 

149.6 

6,000 

44,883.1 

1,000,000 

7,480,519.0 

30 

224.4 

7,000 

52,363.6 

40 

299.2 

8,000 

59,844.1 

From  the  above  any  cubic  feet  reading  can  readily  be  converted  into 
U.  S.  gallons,  as  follows: 

How  many  gallons  are  represented  by  53,928  cubic  feet? 
50,000  cubic  feet  =  374,025.9  gallons. 
3,000       "         "     =    22,441.5         " 
900       "         "     =      6,732.4         " 
20       "         •<     =         149.6         " 


8 


59.8 


53,928  cubic  feet  =  403,409.2  gallons. 


HANDBOOK    ON    ENGINEERING. 


587 


SHOWING   COST  OF  WATER  AT  STATED  RATES 
PER  1OOO  GALLONS. 


Number 
of 
Cubic 
Feet. 

COST  PER  1000  GALLONS. 

5 
Cents. 

6 
Cents. 

8 
Cents. 

10 
Cents 

15 
Cents. 

20 
Cents. 

25 
Cents. 

30 
Cents. 

20 

$0  007 

$0.009 

$0.012 

$0.015 

$0.021 

$0.030         $0.037 

$0.045 

40 

0.015 

0.018 

0.024 

0.030 

0.045 

0060           0-075 

0.090 

60 

0.022 

0.027 

0.036 

0.045 

0.066 

0.090           0.112 

0.135 

80 

0.030 

0.036 

0.048 

0.060 

0.090 

0  120           0.150 

0.180 

100 

0.037 

0.049 

0.060 

0.075 

0.111 

0.150           0.187 

0.224 

200 

0.075 

0.090 

0.120 

0.150 

0.225 

0.299J          0.374 

0.449 

300 

0.112 

0.135 

0.180 

0.224 

0.336 

0  449,          0.561 

0.673 

400 

0.150 

0.180 

0.239)      0.299 

0.450 

0.598           0-748 

0.898 

500 

0.188 

0.224 

0.299 

0.374 

0.564 

0.748 

0-935 

1.122 

600 

0.224 

0.269 

0.359 

0.449 

0.448 

0.898 

1.122 

1-346 

700 

0-262 

0.314 

0.419 

0.524 

0-786 

1.047 

1-309           1-571 

800 

0.299 

0.350 

0.479 

0.598 

0.897 

1.197 

1-496           1-795 

900 

0.337 

0.404 

0.539 

0.673 

1.011 

1  346 

1.683          2-020 

1,000 

0-374 

0.449 

0.598 

0-748 

1-122 

1  496 

1.870 

2.244 

2,000 

0.748 

0.898 

1.197        1.496 

2.244 

2.992 

3-740 

4-488 

3,000 

1.122 

1.346 

1-795 

2-244 

3.366 

4.488 

5.610 

6-732 

4,000 

1.496 

1-795 

2-393 

2.992 

4.488 

5.984 

7.480 

8.976 

5,000 

1.870 

2.244 

2-992 

3-740 

5.610 

7.480 

9-350 

11-220 

6,000 

2.244 

2.692 

3-590 

4-488 

6.732 

8.976 

11.220 

13.464 

7,000 

2.615 

3-141 

4-189 

5-23b 

7.854 

10.472 

13-090 

15.708 

8,000 

2.992 

3.590 

4-787 

5-984 

8-976 

11.9*8 

14.961 

17-953 

9,000 

3.366 

4.039 

5-385 

6.732 

10-098 

13.464 

16-831 

20.197 

10,000 

3.74 

4.488 

5-984 

7-480 

11.122 

14.961 

18.701 

22.441 

20,000 

7.48 

8.976 

11.968 

14.961 

22.443 

29.992 

37-402 

44.882 

30,000 

11.22 

13.46 

17.95 

22-44 

33.664 

44.88 

56.10 

67-32 

40,000 

14-96 

17.95 

23-94 

29.92 

44.885 

59.84 

74-10 

89.77 

50,000 

18.70 

22.44 

29.92 

37.40 

56.103 

74.80 

93-50 

112.20 

60,000 

22.44 

26.92 

35.90 

44.88 

67-323 

89.76 

112.20 

134.64 

70,000 

26.18 

31-41 

41.89 

52-36 

78.543 

104.72 

130.90 

157-08 

80,000 

29.92 

35.90 

47-87 

59.84 

89.766 

119.68 

149.61 

179-53 

90,000 

33.66 

40.39 

53.85 

67-32 

100.986 

134  64 

168-31 

201.97 

100,000 

37.40 

44.88 

59.84 

74.80 

111.22 

149.61 

187-01 

224-41 

200,000 

74.81 

89.76 

119.68 

149.61 

224.43 

299  22 

374.02 

448-82 

300,^00 

112.20 

134.64 

179.53 

224.41 

336.64 

448.83 

561-03 

673.24 

400,000 

149.61 

179.53 

239.37 

299.22 

448-86 

598.44 

748.05 

897-  6H 

500,000 

187.01 

224.41 

299.22 

374.02 

561.03 

748.05 

935.06 

1122-07 

600,000 

224.41 

269.29 

359.06 

448  83 

673-23 

897.66 

1122.07 

1346.49 

700,000 

261.81 

314.18 

418.90 

523.63 

785-43 

1047.27 

1309.08 

1570.88 

800,000 

299-22 

359.06 

478.75 

598.44 

897-66 

1196  88 

1496-10 

1795.32 

900,000 

336.62 

403.94 

538.59 

673.24 

1009-80 

1346.49 

1683.11 

2019.73 

1,000,000 

374.02 

448.83 

598.44 

748.05 

1122.06 

1498.10 

1870.12 

2244.15 

588 


HANDBOOK    ON    ENGINEERING. 


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HANDBOOK    ON    ENGINEERING. 


589 


"  SHOWING  HOW  WATER  MAY  BE  WASTED. 

GALLONS    DISCHARGED    PER    HOUR  THROUGH    VARIOUS    SIZED  ORIFICES 
UNDER    STATED    PRESSURES. 


ca 

S-g 

Diameters  of  Orifices  in  Inches  and  Fractions  of  an  Inch. 

•o  «5 
a  2 



- 

j3  3  o> 

O  05  {2 
p_,  en  « 

4 

I 

4 

1 

1 

1 

U 

j-J 

15 

2 

»-.  cr1 

C«  00 

inch 

inch,inch 

inch 

inch 

inch 

inch 

inch 

inch 

inch 

20 

8.66 

300 

720 

1260 

1920   2760 

4920 

7380 

11100 

15120 

19740 

40 

17.32 

450 

960 

1800 

2760 

3960 

6720 

10920 

15720 

21360 

27960 

60 

25.99 

540 

1200 

2160 

3480   4800 

8580 

13380 

19200 

26220 

34260 

80 

34.65 

620 

1380 

2460 

3840!  5580 

9840 

15480 

22260 

30300 

39540 

100 

43.31 

690 

1560 

2760 

4320!  6240 

11040 

17280 

24900 

33900 

44280 

120 

51.98 

780 

1780 

3000 

4740   6840 

12120 

18960 

27240 

37440 

48480 

140 

60.64 

816 

1860 

3300 

5IOO|  7320 

13020 

20160 

29460 

39080 

52320 

150 

64.97 

840 

1920 

3420 

5280 

7620 

13560 

21180 

30480 

41460 

54120 

175 

75.80 

900 

2040 

3660 

5700 

8220 

14640 

22800 

32880 

44940 

58560 

200 

86.63 

960 

2220 

3900 

6120 

8760 

15600 

25020 

35880 

47880 

62580 

235 

101.79 

1080 

2460 

4320 

8280 

11160 

17100 

26760 

38520 

52260 

68460 

The  pressure  or  head  of  water  is  taken  at  the  orifice,  no  allowance 
being  made  for  friction  in  the  pipe.  In  practical  calculations  to  deter- 
mine the  height  which  water  can  be  thrown,  the  head  consumed  by  the 
friction  of  the  water  in  flowing  from  the  source  to  the  orifice  must  be 
considered. 


IGNITION  POINTS   OF  VARIOUS  SUBSTANCES. 

Phosphorus  ignites  at 150°  Fahr. 

Sulphur-               {?  " 500°      " 

Wood                    "  " 800°      " 

Coal                       »  "                1000°      « 


Lignite,  in  the  form  of  dust,  ignites  at 
Canuel  Coal, 
Coking  <  'oal, 
Anthracite, 


150°  " 

200°  " 

250°  " 

300°  " 


590 


HANDBOOK    ON    ENGINEERING. 


CONTENTS  IN  CUBIC  FEET  AND  IN  U.  S.  GALLONS. 

(FROM    TRAUTWEIN) 

Of  231  cubic  inches  (or  7.4805  gallons  to  a  cubic  foot) ;  and  for  one  foot  of  length  of 
the  cylinder.  For  the  contents  for  a  greater  diameter  than  any  in  the  table  take 
quantity  opposite  one  -half  said  diameter,  and  multiply  it  by  4.  Thus,  the  number 
of  cubic  feet  in  one  foot  length  of  a  pipe  80  Inches  In  diameter  is  equal  to 
8.728X4=34.912  cubic  feet.  So  also  with  gallons  and  areas. 


For  1  foot  in 

For  1  foot  in 

For  1  foot  in 

c 

M 

length. 

S  ^ 

a  <* 

length. 

c 

M<H 

length. 

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22.58 

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2.000 

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23.50 

15-16 

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2.083 

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25.50 

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2.166 

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4.276 

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4.498 

29. 

2  416 

4  587 

34.31 

2, 

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3 

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4.714 

30 

2.500 

4.909 

36.72 

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11. 

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| 

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£ 

9583 

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5  395 

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12. 

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5  876 

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9.180 

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i 

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1.310 

9.801 

42. 

3.500 

9.620 

71.96 

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3.583 

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75.43 

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1650 

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1.485 

11.11 

44. 

3  666 

10.560 

79  00 

| 

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17. 

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11.79 

45. 

3.750 

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82  62 

6. 

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12.50 

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18. 

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4.000 

12.566 

94.02 

HANDBOOK    ON    ENGINEERING.  591 


CHAPTER    XX. 
THE  INJECTOR  AND  INSPIRATOR. 

The  energy  of  motion  of  a  body  is  well  known  to  be  the  prod- 
uct of  its  mass  by  the  half  square  of  its  velocity ;  hence,  it  is 
possible  to  communicate  to  a  body  of  little  weight  a  large  amount 
of  energy  by  moving  it  fast  enough,  and  in  fact,  the  energy  of 
motion  would  only  be  limited  by  the  speed  which  can  be  given 
the  body.  In  this  way  a  small  weight  of  steam  flowing  from  an 
orifice  into  a  properly  shaped  jet  of  water  is  condensed,  while  the 
velocity  of  the  steam  is  greater  than  if  flowing  into  air ;  the 
energy  thus  communicated  is  made  sufficiently  great  by  increasing 
the  weight  of  steam,  which  can  be  done  by  increasing  the  area  of 
the  steam  way,  until  we  find  such  jet  pumps  adapted  to  many 
purposes.  There  are,  however,  two  which  are  of  interest  to  us 
in  this  connection,  the  well-known  injector  and  inspirator,  with 
the  large  family  of  lifting  and  non-lifting  varieties,  all  differing 
in  details  as  to  form  of  nozzles,  area  of  passages,  distances 
between  nozzles,  and  that  class  of  instruments  in  which,  after  a 
certain  energy  and  velocity  have  been  reached,  the  operation  is 
repeated.  These  might  be  called  "  consecutive  "  instruments. 
The  illustrations  in  this  book  show  some  of  the  simplest  and 
adjustable  kinds.  Within  a  few  years  the  principle  of  increase  of 
energy  by  increase  of  mass  or  velocity  has  been  applied  by  in- 
creasing the  mass  of  steam  used  until  we  find  that  not  only  can  a 
few  pounds  weight  of  steam  put  into  a  boiler  a  good  many  more 
pounds  of  water  at  a  much  higher  temperature  than  it  had,  but 
that  in  a  non-condensing  engine  it  is  possible,  by  using  the  ex- 
haust in  part,  to  put  into  the  boiler  at  a  much  higher  pressure 


592  HANDBOOK    ON    ENGINEERING. 

and  temperature,  a  weight  of    water  which  is  still    greater   tlian 
that  of  the  steam  moving  it. 

When  the  injector  first  made  its  appearance  it  was,  by  many, 
considered  as  almost  a  paradox,  especially  by  those  who  looked 
at  the  question  as  one  of  hydrostatics  only.  That  steam  from  a 
boiler  could  put  water  back  into  it  at  the  same  pressure,  and  over- 
come the  friction  of  the  passages  without  the  aid  that  a  steam 
pump  had  of  a  difference  of  piston  areas,  was  to  them  a  puzzle. 
The  use  of  exhaust  steam  at  atmospheric  pressure  for  the  purpose 
of  putting  water  into  a  boiler  at  a  pressure  of  150  Ibs.  per  square 
inch,  would  be  to  such  minds  utterly  incomprehensible.  The  use 
of  an  injector  and  inspirator,  has  this  to  recommend  them,  that 
the  feed-water  cannot  be  introduced  into  the  boiler  cold  or  nearly 
so,  but  must  be  warmed  by  contact  with  the  steam,  and  the  value 
of  this  has  been  already  shown.  In  small  boilers  where  no  heater 
is  used,  an  exhaust  injector  is  better  than  a  pump,  and  so  is  an 
ordinary  injector ;  but  the  former  includes  in  itself  an  exhaust 
heater,  saving  a  portion  of  heat  from  the  exhaust,  besides  taking 
the  power  as  heat  also ;  while,  with  the  common  injector,  the 
heat  for  power  and  raising  temperature  are  both  derived  from  the 
live  steam  in  the  boiler.  The  latter  portion  of  heat  is,  of  course, 
directly  returned  to  the  boiler  without  loss,  but  that  for  power  is 
necessarily  expended.  As  to  the  amount  of  power  used  by  pump 
and  injector  compared  with  each  .other,  it  would  seem  that  the 
pump  is  most  efficient.  There  have  been  many  comparative  trials 
of  pump  and  injector,  but  the  results  have  usually  been  unsatis- 
factorv  from  contained  discrepancies. 

RANGE  OF  THE  INSPIRATOR  AND  INJECTOR. 

The  steam  pressure  at  which  an  injector  will  start  and  the 
highest  steam  pressure  at  which  it  will  work  constitute  what  is 
termed  the  "  range  "  of  an  injector,  and  the  inspirator  varies  with 
the  vertical  lift  and  the  temperature  of  the  feed  water. 


HANDBOOK    ON    ENGINEERING. 


It  must  also  be  borne  in  mind  that  the  same  style  of  construc- 
tion in  an  injector  and  inspirator,  while  it  confines  them  to  about  a 
specific  range  between  its  lowest  starting  and  highest  working  points, 
permits  of  variation  as  to  what  the  lowest  starting  point  shall  be. 
A  style  of  construction  which  gives  a  range  (on  say  a  2-foot  lift) 
of  25  Ibs.  to  155  Ibs.  would  permit  of  a  range  of  35  Ibs.  to  165 
Iks.  (in  fact,  to  a  little  higher  than  165  Ibs.).  Different  manu- 
facturers, therefore,  vary  as  to  the  starting  point  in  their  stand- 
ard machines  —  aiming  to  cover  the  range  which  they  deem  most 
desirable.  Nearly  all  have  adopted  about  25  Ibs.  on  a  2-foot  lift, 
as  lowest  starting  point. 


The  World. 


POSITIVE  OR  DOUBLE  TUBE  INJECTORS. 

As  before  stated,  this  class  of  injector  is  provided  with  two  sets 
of  tubes  or  jets,  one  set  adapted  to  lift  the  water  and  deliver  it  to 

88 


594  HANDBOOK    ON    ENGINEERING. 

the  second  set,  which  forces  the  water  into  the  boiler.  By  this 
arrangement,  it  is  apparent  that  inasmuch  as  the  lifting  jets 
supply  a  proportionate  amount  of  water  with  varying  steam  pres- 
sures, a  wider  range  is  obtainable  than  with  an  automatic  in- 
jector. In  the  following  cases,  it  is  better  to  use  the  double  tube 
injectors : — 

1.  Where  the  feed  water  is  of  too  high  a  temperature  to  be 
handled  by  the  automatic  injectors. 

2.  When   a  great  range  of  steam   variation  is  accompanied  by 
the  condition  of  a  long  lift. 

The  World  Injector  is  one  of  the  best  and  most  popular  of  the 
double  tube  type  of  injectors.  It  is  entirely  self  contained.  It 
is  supplied  even  with  its  own  check  valve  and  operated  entirely 
by  a  single  lever,  a  quarter  of  a  turn  of  which  starts  the  lifting, 
after  which  the  completion  of  the  single  revolution  sets  the  injector 
working  to  boiler. 

GENERAL  SUGGESTIONS  FOR  PIPING=UP  INJECTORS  AND 
INSPIRATORS  AND  SUGGESTIONS  THAT  SHOULD  BE 
CAREFULLY  FOLLOWED  WHEN  MAKING  PIPE  CONNEC= 

TIONS. 

i 

Steam*  —  Connect  steam  pipe  with  highest  parts  of  boiler  and 
never  connect  with  a  steam  pipe  used  for  any  other  purpose.  I 
would  recommend  a  globe  valve  being  placed  in  the  steam  pipe 
next  to  boiler  which  can  be  closed  in  case  it  is  desired  to  take  off 
the  injector.  At  all  other  times  it  can  be  left  open.  When  the 
steam  connection  is  made,  be  sure  and  take  off  the  injector  before 
the  steam  is  turned  on  the  machine.  Then  blow  out  the  steam 
pipe  with  at  least  forty  pounds  steam,  which  will  remove  all  dirt 
and  scale. 

Suction*  —  This  pipe  must  be  tight,  and  if  there  is  a  valve  in  it 
the  stem  must  be  well  packed. 

To  test  the  suction  pipes  for  leaks,  plug  up  the  end  of  the  pipe 


HANDBOOK    ON    ENGINEERING. 


595 


and  then  screw  on  a  common  iron  cap  on  the  overflow  ;  or  if  you 
do  not  have  one,  unscrew  cap  X,  and  place  a  piece  of  wood  on 
top  of  valve  P;  replace  the  cap  and  the  wood  will  hold  the  valve 
from  rising ;  then  turn  on  the  steam  which  will  locate  all  leaks. 


All  pipes,  whether  steam,  suction  or  delivery,  must  be  of  the 
same  or  greater  size  than  the  corresponding  branch  of  each  injec- 
tor. Have  all  piping  as  short  and  as  straight  as  possible,  and 
especially  avoid  short  turns. 


59 ()  HANDBOOK    ON    ENGINEERING. 

If  any  old  pipe  is  used,  see  that  it  is  not  partially  filled  or 
stopped  up  with  rust. 

If  the  injector  or  inspirator  has  to  lift  the  water  very  high  or 
draw  it  very  far,  have  the  suction  pipe  a  size  or  two  larger  than 
called  for  by  the  suction  branch  of  the  injector  or  inspirator. 

Have  the  water  supply  (suction)  pipe  independent  of  any  other 
connection.  ,  The  suction  pipe  must  be  absolutely  air  tight ;  the 
slightest  leak,  in  most  cases,  will  prevent  the  injector  or  inspirator 
from  forcing  water  into  the  boiler. 

Always  place  a  globe  valve  in  the  suction  pipe  as  close  to  the 
injector  as  possible,  and  place  it  so  that  it  will  shut  down  against 
the  water  side  and  see  that  the  stem  is  packed  tight. 

When  using  the  injector  or  inspirator  as  NON-LIFTING;,  put  two 
globe  valves  in  the  suction,  one  close  to  the  injector,  the  other  us 
far  from  it  as  you  can  conveniently,  keeping  the  one  farthest  from 
the  injector  or  inspirator  tolerably  close  throttled.  This  will 
surely  repay  you  for  your  trouble.  The  check  valve  may  be  next 
to  boiler  with  a  valve  between  it  and  boiler,  the  further  from 
injector  the  better.  If  the  injector  forces  through  a  heater,  place 
check  valve  between  injector  and  heater.  Also  place  a  valve 
between  heater  and  check  valve  so  you  can  take  check  valve  out 
if  necessary. 

Size  of  pipes*  —  If  injector  or  inspirator  has  over  10  feet  lift, 
or  a  long  draw,  use  suction  pipe  from  strainer  to  valve  a  size 
larger  than  the  connection  on  injector,  reducing  when  you  reach 
the  valve. 

In  all  other  cases,  use  for  all  pipes  same  size  as  injector 
connection. 

Blow-off*  —  Always  blow  out  steam  thoroughly  BEFORE  CON- 
NECTING INJECTOR,  so  as  to  remove  any  dirt,  rust  or  scale  that 
may  be  in  the  pipes. 

Caution*  —  The  suction  pipe  must  be  ABSOLUTELY  TIUHT 
throughout.  To  make  sure  that  it  is  so,  test  the  suction  as  directed. 


HANDBOOK    ON    ENGINEERING.  597 

DIRECTIONS   FOR  CONNECTING  AND  OPERATING  THE 
HANCOCK  INSPIRATOR. 

41  Stationary "  Pattern. —  Connect  as  shown  by  cut  above 
steam,  suction  and  delivery.  For  full  instructions,  see  page  588. 

For  a  lift  of    5  ft.,  15  Ibs.  steam  pressure  is  required. 
"        »4         10  "     20    "        "  "  " 

"        "         15   "     25    'l         "  "  tl 

"        "         20  "     35    "         "  "  " 

"        "         25  "     45    "        "  "  " 

Operation*  —  Open  overflow  valves  Nos.  1  and  3  ;  close  forcer 
steam  valve  No.  2  and  open  the  starting  valve  in  the  steam  pipe. 
When  the  water  appears  at  the  overflow,  close  No.  1  valve ;  open 
No.  2  valve  one-quarter  turn  and  close  No.  3  valve.  The  inspir- 
ator will  then  be  in  operation. 

NOTE.  —  No.  2  valve  should  be  closed  with  care  to  avoid  damag- 
ing the  valve  seat.  When  the  inspirator  is  not  in  operation,  both 
overflow  valves  Nos.  1  and  3  should  be  open  to  allow  the  water  to 
drain  from  it.  No  adjustment  of  either  steam  or  water  supply  is 
necessary  for  varying  steam  pressures,  but  both  the  temperature 
and  quantity  of  the  delivery  water  can  be  varied  by  increasing  or 
reducing  the  water  supply.  The  best  results  will  be  obtained 
from  a  little  experience  in  regulating  the  steam  and  water  supply. 
If  the  suction  pipe  is  filled  with  hot  water,  either  cool  off  both  it 
and  the  inspirator  with  cold  water,  or  pump  out  the  hot  water  by 
opening  and  closing  the  starting  valve  suddenly.  To  locate  a  leak 
in  the  suction  pipe,  plug  the  end,  fill  it  with  water,  close  No.  3 
valve  and  turn  on  full  steam  pressure.  Examine  the  suction  pipe 
and  the  water  will  indicate  the  leak.  If  the  inspirator  does  not 
lift  the  water  properly,  see  if  there  is  a  leak  in  the  suction  pipe. 
Note  if  the  steam  pressure  corresponds  to  the  lift  as  above  speci- 
fied, and  if  the  sizes  of  pipe  used  are  equal  in  size  to  inspirator 
connections.  If  the  inspirator  will  lift  the  water,  but  will  not  de- 
liver it  to  the  boiler,  see  if  the  check  valve  in  the  delivery  pipe  is 


598 


HANDBOOK    ON     ENGINEERING. 


in  working  order  and  does  not  "  stick."  Air  from  a  leak  in  the 
suction  connections,  will  prevent  the  inspirator  from  delivering 
the  water  to  the  boiler,  even  more  than  it  will  in  lifting  it  only.  If 
No.  1  valve  is  damaged,  or  leaks,  the  inspirator  will  not  work 
properly.  No.  1  valve  can  be  easily  removed  and  ground. 

THE    HANCOCK    STATIONARY    INSPIRATOR. 


STEAM 


Feed  to 
Boiler. 


Suction. 


WATER 


Overflow. 

To  remove  scale  and  deposits  from  inspirator  jets  or  parts, 
disconnect  the  inspirator  and  plug  both  the  suction  and  delivery 
outlets  with  corks.  Open  No.  2  valve  and  fill  the  inspirator  with 
a  solution  of  one  part  muriatic  acid  and  ten  parts  water.  Allow 
this  solution  to  remain  in  the  inspirator  over  night,  then  wash  it 
thoroughly  in  clear  water. 

NOTE.  —  It  is  not  gerierally  necessary  to  return  an  inspirator 
for  repairs.  The  repair  parts  required  can  be  ordered  and  the 
inspirator  readily  put  in  order. 


HANDBOOK    ON    ENGINEERING.  599 


TO   DISCOVER   CAUSE   OF   DIFFICULTIES. 

WHEN    INJECTOR    FAILS    TO    GET    THE    WATER. 

1.  The  supply  may  be  cut  off  by:   (a)  Absence  of  water  at  the 
source,     (b)  Strainer  clogged  up.     (c)  The  suction  pipe,  hose 
or  valve  stopped  up ;  or  if  a  hose  is  used,  its  lining  may  be  loose 
(a  frequent  cause  of  trouble). 

2.  A  large  leak  in  the  suction  (note  that  a  small  leak  will  pre- 
vent injector  from  working,  but  not  from  getting  the  water). 

3.  Suction    pipe    or    water    very    hot.     Open    drip-cock,   turn 
steam  on  slowly,  then  shut  it  off  quickly.     This  will  cause  the 
cool  air  to  rush  into  the  suction  pipe  and  cool  it  off.     Repeat  if 
necessary. 

4.  Lack  of  steam  pressure  for  the  lift;  or,  in   some  instances, 
too  much  steam  pressure.     If  the  steam  pressure  is  venr  high,  the 
injector  will  get  the  water  more  readily  if  the  steam  is  turned  on 
slowly  and  the  drip-cock  left  open  until  the  water  is  got. 

IF      THE     INJECTOR     GETS    THE    WATER    BUT    DOES    NOT    FORCE    IT    TO 

THE    BOILER. 

1.  No   globe  valve  on  the  suction   with  which  to  regulate  the 
water,  or  else  the  supply  water  not  properly  regulated. 

2.  Dirt  in  delivery  tube. 

3.  Faulty  check  valve. 

4.  Obstruction  between   injector   and  check  valve,  or  between 
check  valve  and  boiler. 

5.  Small    leak  in  suction  pipe  admitting  air    to    the    injector 
along  with  the  supply  water.     It  is  ten  to  one  this  is  the  cause  of 
the  difficulty  every  time. 

6.  Be    sure  you  understand  the   directions  for  starting  before 
you  condemn  the  injector. 


600 


HANDBOOK    ON    ENGINEERING. 


IF    THE    INJECTOR    STARTS    BUT     "  BREAKS." 


1.  Supply  water  not  properly  regulated.     If  too  much  water, 
the  waste  or  overflow  will  be  cool;  if  too  little,  the  water  will  lie- 
very  hot. 

2.  Leaky    supply  pipe  admitting  air  to  the  injector.      It  is  ten 
to  one   this  is  the  cause  of  difficulty.     The  suction  must  be  air 
tight;  test  as  directed. 


MODE  OF 
CONNECTING 


The  above  illustration  shows  the  mode  of  connecting  the  Pen- 
berthy   Injector. 

3.  Dirt   or    other  obstruction,   such   as   lime,  etc.,  in  delivery 
tube.    . 

4.  Connecting    steam  pipe  to   pipe   conducting  steam  to  other 
points    besides    the  injector,  or    not    having  suction  pipe    inde- 
pendent. 


HANDBOOK    ON    ENGINEERING. 


fiOl 


f>.  Sometimes  a  globe  valve  is  used  on  the  suction  connection 
that  has  a  loose  disc,  and  after  starting  the  disc  is  drawn  down, 
thus  partially  closing  the  valve;  it  is,  of  course,  equivalent  to 
giving  the  injector  too  little  water.  To  remedy  this,  take  the 
globe  valve  off  and  reverse  it  end  for  end. 

To  clean*  —  To  clean  injector,  unscrew  plug  O,  and  the  re- 
movable jet  Y  (which  rests  in  it)  will  follow  the  plug  out. 
Turn  on  steam  (not  less  than  forty  pounds)  and  all  dirt  will  be 
blown  out.  Examine  all  passages  and  drill  holes  and  see  that  no 
dirt  or  scale  has  lodged  in  them.  Replace  jet  by  setting  it  in  the 
plug  (which  acts  as  a  guide)  and  screw  into  place  tightly.  Be 
c  ireful  not  to  bruise  any  jets,  and  use  no  wrenches  on  body  of 
injector. 

PRICE  LIST,  CAPACITY,  HORSE   POWER,  ETCo 


Size. 


Price. 


Pipe  Connections. 


Capacity  per  Hour. 

1  to  4  ft.  lift,  50  to  75 

Ibs.  Pressure. 


Horse 
Power. 


Steam.  Suction.  Delivery, 

Maximum.  :  Minimum. 

OO.   . 
A  

$16  00             *      §  i 

18  00                    i 

n. 

30  g 
120 

al.    55  gal. 
70  " 

4  to   8 
8  to  10 

A  A  

20  00                    A 

165 

90  " 

10  to  15 

B  

25  00                    | 

250 

135 

15  to  25 

lili   . 

30  00                    ; 

340 

165 

25  to  35 

C  

40  00      1 

475 

300 

35  to  50 

cc.  .. 

45  00     1 

575 

350 

50  to  60 

D  

55  00      i 

750 

400 

60  to  95 

DD  .. 

HO  00  i    J 

920 

500 

95  to  162 

E  

75  00      £ 

1300 

700 

120  to  150 

EK  . 

90  00  i    H 

1740 

900 

\  165  to  230 

F  

110  00     2"       2"      2 

2270 

1100 

230  to  290 

FP  

125  00     2       2     -  2 

2820 

1400 

1  290  to  365 

! 

To  test  for  leaks, —  Plug  up  end  of  water  supply  pipe,  then 
fit  a  piece  of  wood  into  cap  Z,  so  that  when  screwed  down  it  will 
hold  the  valve  P  in  place,  then  turn  on  steam  and  it  will  locate 
leak.  Do  not  fail  to  do  tli,i$  in  case  of  any  trouble. 


TO    START    AND    STOP    INJECTOR. 


To  start* — Open  full  the  globe  valve  in  water  supply  first, 
and  then  globe  valve  in  steam  pipe  wide  open.  If  water  issues 
from  overflow,  throttle  the  valve  //until  discharge  stops.  Reg- 


602 


HANDBOOK    ON    ENGINEERING. 


ulate  injector  with  water  supply  valve,  not  by  steam  valve. 
When  water  supply  is  above  the  injector,  in  starting  open  steam 
valve  first. 

To  stop* — Close  the  steam  valve.  The  water  valve  H  need 
not  be  closed  unless  the  injector  is  used  as  a  non-lifter,  or  lift  is 
considerable. 

The  following  table  gives  the  number  of  British  thermal  units  in  a  pound  of  water 
at  different  temperatures.  They  are  reckoned  above  32  degs.  Fan.,  because,  strictly 
speaking,  water  does  not  exist  below  32  degs.  Fan.,  and  ice  follows  another  law. 

WATER    BETWEEN    32°    AND    212°    FAH. 


0 

i 

<o 

j 

0 

1 

o> 

J 

0 

~ 

1 

"•d 

5 

10  'd 

s 

""•d 

. 

2 

-a 

2  1 

flg 

2  o 

2 

a§ 

S  1 

2 

c  g 

5  1 

9 

•~^  o 

5  ** 

o 

•^  '  O 

•d  *** 

0 

fc| 

V 

^  o 

s  ^ 

P< 

-*J  a 

60   O 

~ 

**  " 

%  •- 

a 

4->  a 

"bC   O 

Pta 

—  a 

bo  w 

a  a 

83  l_i 

~*   •  — 

S  £ 

OJ  .. 

S-q 

55  t. 

7*   *^ 

Sa 

rfn 

T  Lrf  13 

0)  :3 

«  £ 

QJ  gj 

w  5 

*  03  "5 

<y  5 

0>  si 

«  £ 

Ba 

^  ao 

-  a 

£a§ 

££ 

3a 

£a« 

Hfc 

Ba 

£a« 

32^ 

0  00 

62.4-2 

110° 

78  00 

61.89 

115° 

1'3  26 

61.28 

179° 

147.  at 

60  57 

35 

3.02 

62.42 

112 

80  00 

61  86 

146 

114  27 

61.26 

180 

148.54 

60  55 

40 

8.06 

62.42 

113 

81  01 

61.84 

147 

115  2o 

61.24 

181 

149.55 

60.53 

45 

13.08 

62  42 

114 

82.02 

61  83 

148 

116  29 

61.22 

182 

150.56 

60  50 

50 

18.10 

62.41 

115 

83.02 

61  82 

149 

117  30 

61.20 

183 

151  57 

60.48 

52 

20.11 

62  40 

116 

84.03 

61  80 

150 

118  30 

61.18 

184 

152  58 

60.46 

54 

22.11 

62.40 

117 

85.04 

61  78 

151 

119  31 

61.16 

185 

153  58 

60  44 

56 

24  11 

62  39 

118 

86  05 

61.77 

152 

120  32 

61.14 

186 

154  59 

60  41 

58 

26.12 

62  38 

119 

87.06 

61  75 

153 

121  33 

61.12 

187 

155  60 

60.39 

60 

28  12 

62.37 

120 

88.06 

61  74 

154 

122.34 

61.10 

188 

156  61 

60.37 

62 

30  .  12 

62.36 

121 

89  07 

61  72 

155 

123.34 

61.08 

189 

157  62 

60.34 

64 

32.12 

62  35 

122 

90.08 

61.70 

156 

124  35 

61.061 

190 

158  62 

60.32 

66 

34  12 

62  34 

123 

91.09 

61.08 

157 

125.36 

61.04 

191 

159.63 

GO  29 

63 

36.12 

62.33 

124 

92  10 

61.67 

158 

126.37 

61.02! 

192 

160.63 

60  27 

70 

3«  11 

H2  31 

125 

93  10 

61  65 

159 

127.38 

61.00 

193 

161.64 

60  25 

72 

40.11 

62.30 

126 

94  11 

61.63 

160 

128  38 

60.98 

194 

162  65 

60  22 

74 

42.11 

62  28 

127 

95  12 

61.61 

161 

129  39 

60.96 

195 

163.66 

60.20 

76 

44  11 

32.27 

128 

96.13 

61  60 

162 

130  40 

60.94 

196 

164.66 

60  17 

78 

46  10 

62.25 

129 

97.14 

61.58 

163 

131.41 

60.92 

197 

165.67 

60  15 

80 

43.09 

62.23 

130 

98  14 

61.56 

164 

132.42 

60.90 

198 

166.68 

60.12 

82 

50.08 

02.21 

131 

99  15 

61.54 

165 

133.42 

60.87 

199 

167.69 

60  10 

84 

52.07 

62.19 

132 

100.16 

61.52 

166 

134  43 

60.85 

200 

168.70 

60.07 

86 

54  06 

62  17 

133 

101.17 

61  51 

167 

135.44 

60.83 

201 

169.70 

60.05 

88 

56  05 

62.15 

134 

102  18 

61.49 

168 

136.45 

60.81 

202 

170  71 

60.02 

90 

53  04 

62.18 

135 

103.18 

61.47 

169 

137.  4K 

60.79 

203 

171  72 

60.00 

92 

60.03 

62  11 

136 

104  19 

61.45 

170 

138.46 

60.77 

204 

172.73 

59.97 

94 

62  02 

62.09 

137 

105.20 

61.43 

171 

139  47 

60.75 

205 

173.74 

59.95 

96 

64  01 

62  07 

138 

106.21 

61.41 

172 

140  48 

60.73 

206 

174  74 

59  92 

98 

66  01 

62.05 

139 

107.22 

61.39 

173 

141.49 

60.70 

207 

175.75 

59  89 

100 

68.01 

62  02 

140 

103  22 

61.37 

174 

142  50 

60  68 

208 

176  76 

59  87 

102 

70.00 

62  00 

141 

109.23 

61  36 

175 

143.50 

60.66 

209 

177.77 

59.84 

104 

72.00 

61.97 

142 

110  24 

61  34 

176 

144.51 

60.64 

210 

178.78 

59.82 

106 

74.00 

61.95 

143 

111  25 

61  32 

177 

145.52 

60.62 

211 

179.78 

59.79 

108 

76  00 

61.92 

144 

112.26 

61.30 

178 

146  53 

60.59 

212 

180.79 

59  76 

HANDBOOK    ON    ENGINEERING.  603 

To  find  the  number  of  gallons  of  water  delivered  by  a  steam 
pump  in  one  minute,  when  the  diameter  and  stroke  of  water 
piston,  and  the  number  of  strokes  per  minute  are  given :  — 

Rule*  —  Square  the  diameter  of  water  piston  and  multiply  the 
result  by  .7854.  Multiply  this  product  by  the  stroke  of  the 
water  piston  in  inches ;  and  multiply  this  product  by  the  number 
of  strokes  per  minute,  and  divide  the  result  by  231. 

Example* — How  many  gallons  of  water  per  minute  will  a 
steam  pump  deliver,  whose  water  cylinder  is  6  inches  in  diameter 
and  12  inches  stroke,  making  60 strokes  per  minute? 

Ans.  88.128  galls. 

Operation  :  6  X  6  X  .7854       28.2744. 

28.2744  X  12  X  60 
And,  -~23i~         -  =  88.128. 

To  find  the  relative  proportion  between  the  steam  and  water 
pistons. 

Rule*  —  Multiply  the  area  of  the  pump  piston  by  the  resistance 
of  the  water  in  pounds  per  square  inch ;  and  divide  the  product 
by  the  pressure  of  steam  in  pounds  per  square  inch.  The  quotient 
will  give  the  area  of  steam  piston  in  square  inches  to  balance  the 
resistance.  To  this  quotient  add  from  30  to  100  per  cent  of  it- 
self,—  depending  on  the  speed  of  the  pump,  —  and  divide  the 
sum  by  .7854,  and  extract  the  square  root  of  the  quotient  for  the 
diameter  of  the  steam  piston. 

Example*  —  What  should  be  the  diameter  of  the  'steam  piston 
to  force  water  against  a  pressure  of  125  pounds  per  square  inch, 
the  diameter  of  water  piston  being  6  ins.  and  the  steam  pressure 
60  Ibs.  per  square  inch?  Ans.  10J  inches. 

Operation:  6X6       .7874  =  28.2744  sqr.  ins. 

And,  28.2744  X  125  =  3534.3  pounds  the  total  resistance. 

3534.3 
Then,   — :^r —  =  58.9  square  inches  the  area  of  steam  piston. 


604  HANDBOOK    ON    ENGINEERING. 

We  will  add  50  per  cent  for   friction  in  pump  and  in  delivery 
pipe,  and  for  a  moderate  speed  of  pump. 
Then,  58.0  X  .50  =  29.45. 
And,  58.1)  +  29.45=88.35, 

88.35 
And,      r-vKA  =  112.49  sqr   ins. 


Then,  ^J  112.49  =  10.6  ins.  the  diameter  of  the  steam  piston. 

To  find  the  pressure  against  which  a  pump  can  deliver  water, 
when  the  diameter  of  steam  piston,  pressure  of  steam  in  pounds 
per  square  inch,  and  diameter  of  water  piston  are  given :  — 

Rule*  —  Multiply  the  area  of  steam  piston  by  the  pressure  of 
steam  in  pounds  per  square  inch,  and  divide  the  product  by  the 
area  of  the  pump  piston,  and  deduct  from  30  to  50  per  cent  for 
friction  in  the  delivery  pipe  and  in  the  pump  itself. 

Example* — The  area  of  the  steam  piston  is  112  square  inches, 
and  the  area  of  water  piston  is  28  square  inches,  and  the  steam 
pressure  is  60  Ibs.  per  square  inch,  against  what  pressure  can  the 
pump  deliver  water,  the  resistance  from  friction  being  48  per  cent? 

Ans.  125  Ibs.  per  sqr.  in.,  nearly. 

112X60 
Operation: gg— 

And,  240  X  -48  =  115.20. 
Then,  240  —  115.20  =  124.8. 

To  find  the  steam  pressure  required  when  the  diameter  of  the 
steam  piston,  the  diameter  of  the  water  piston,  and  the  resistance 
against  the  pump  in  pounds  per  square  inch  are  given :  — 

Rule. —  Multiply  the  area  of  water  piston  by  the  resistance  on 
the  pump  in  pounds  per  square  inch,  and  divide  the  product  by 
the  area  of  the  steam  piston. 


HANDBOOK    ON     ENGINEERING.  605 

Example*  —  The  resistance  against  the  pump,  including  fric- 
tion, is  240  pounds  per  square  inch.  The  area  of  steam  piston 
is  112  square  inches,  and  the  area  of  water  piston  is  28  square 
inches.  What  pressure  of  steam  is  required  to  operate  the  pump? 

Ans.   60  Ibs.  per  sqr«  in. 

~  240  X  28       ,n 

Operation:  —  —    -  =  60. 

LL4 

Now  anything  over  60  Ibs.  will  operate  the  pump,  and  the  faster 
it  is  run  the  higher  must  be  the  pressure  above  60  pounds. 

To  find  the  diameter  of  water  piston  when  the  diameter  of 
steam  piston,  the  steam  pressure  in  pounds  per  square  inch,  and 
the  resistance  against  the  pump  piston  in  pounds  per  square  inch 
are  given  :  — 

Rule.  —  Multiply  the  area  of  steam  piston  in  square  inches  by 
the  steam  pressure  in  pounds  per  square  inch,  and  divide  the 
product  by  the  resistance  in  pounds  per  square  inch  on  the  water 
piston. 

Example*  —  The  resistance  against  the  pump,  including  fric- 
tion, is  240  pounds  per  square  inch  ;  the  area  of  steam  piston  is 
112  square  inches,  the  steam  pressure  is  60  pounds  per  square 
inch,  what  should  be  the  diameter  of  water  piston? 

Ans.  6  inches. 

Operation  :  -      X  6°  =  35.65  sqr.  ins.        Call  it  36  sqr.  ins. 


Then,  ^        =  6. 

To  find  the  horse  power  required  in  a  steam  pump  to  feed  a 
boiler  with  a  given  number  of  pounds  of  water  per  hour  against  a 
given  pressure  of  steam  :  — 

Rule.  —  Multiply  the  velocity  of  flow  of  water  in  feet  per  min- 
ute by  the  total  pressure  against  which  the  water  is  pumped  in 
pounds  per  square  inch,  and  divide  the  product  by  33,000,  and 
the  quotient  will  be  the  horse  power. 


606  HANDBOOK    ON    ENGINEERING. 

Example*  —  What  horse  power  is  required  to  feed  a  boiler 
with  600  gallons  of  water  per  hour  against  a  total  resistance  of 
112  Ibs.  per  square  inch,  including  the  friction  in  the  delivery 
pipe,  lift  of  water  in  suction  pipe,  weight  of  check  valve,  and 
friction  in  the  pump  itself?  Ans.  1  H.  P.  nearly. 

Operation:  600  X  231  =  138,600  cubic  inches  of  water  per 
hour. 

138,600 
And,      — gQ —    =2310  cubic  inches  of  water  per  minute. 

2310 
And,    — :-£— =192.5    feet     per    minute,    the    velocity    of  the 

water. 

The  total  resistance  is  112  Ibs.  per  sqr.  in. 
Then,  192.5  X  112  =  21560  foot  pounds. 

21560 
And'     3^000  =  -663H.P. 

Now  add  say  50  'per  cent  and  we  have  .653  X  .50  =  .3265. 
And,  . 653 -f  .3265  =  .9795. 

This  pump  will  feed  a  boiler  as  shown  above,  or  it  will  deliver 
600  gallons  of  water  per  hour  under  a  head  of  258  feet. 

112 
Thus,    -^^  =  258. 

To  find  the  horse-power  of  boiler  required  to  furnish  steam  for 
a  pump  running  at  its  fullest  capacity. 

Role*  —  Multiply  the  number  of  gallons  of  water  delivered  by 
the  pump  in  one  minute  by  8-J.  Multiply  this  product  by  the 
total  height  in  feet  to  which  the  water  is  to  be  lifted,  measuring 
vertically  from  the  source  of  supply  to  the  point  of  delivery,  and 
divide  the  result  by  33,000.  Add  from  50  to  75  per  cent  to  the 
quotient  for  loss  from  friction  of  water  in  the  pipe,  friction  in 
the  pump,  waste  of  steam  in  the  cylinder,  and  other  contingencies, 
aud  the  result  will  give  the  horse  power  of  boiler  required. 


HANDBOOK    ON    ENGINEERING.  607 

Example*  —  What  horse-power  of  boiler  is  required  to  run  a 
steam  pump  lifting  800  gallons  of  water  per  minute  to  a  height  of 
103  ft.  from  the  source  of  supply?  Ans.  50  H.  P.,  nearly. 

Operation  :  800  X  8J  =  6667  Ibs.  of  water. 

And,  6667  X  163  =  1,086,721  footpounds. 

1,086,721 
And,     ---    -  33  H.  P.,  nearly. 


Then,  33  X  .50=16.50. 
And,  33  -f  16.5  =  49.5. 

To  find  the  diameter  of  discharge  nozzle  for  a  steam  pump, 
when  the  diameter  and  stroke  of  the  water  piston  and  the  number 
°f  strokes  per  minute  are  given,  and  the  maximum  flow  of  water 
in  feet  per  minute  is  given  :  - 

Rule*  —  Find  the  cubic  contents  of  the  water  cylinder  for  one 
stroke  in  cubic  feet,  and  multiply  it  by  the  number  of  strokes  per 
minute.  Multiply  this  product  by  144  and  divide  the  result  by 
the  velocity  of  the  water  in  feet  per  minute,  and  the  quotient  will 
be  the  area  of  pump  nozzle  in  square  inches. 

Example*  —  The  diameter  of  water  cylinder  is  10  inches,  and 
the  stroke  of  piston  is  12  inches,  and  the  speed  is  50  strokes  per 
minute.  The  velocity  of  water  required  is  500  feet  per  'minute, 
what  should  be  the  diameter  of  pump  discharge  nozzle  ? 

Ans.  3  J  ins.,  nearly. 

Operation:  10  X  10  X  .7854  =  78.54  sqr.  ins.  area  of  piston. 

And,  78.54  X  12  =  942.48  cubic  inches  in  the  cylinder  for  one 
stroke. 

942.48 
And,    -  ^pft    =  .5454  of  a  cubic  foot  for  one  stroke. 

And,  .5454  X  50  ==  27.27  cubic  feet  for  50  strokes  per  minute. 

27.27  X  144 

Then,   -    —  ^TTX—  -  =  7.8537  sqr.  ins.  the  area  of  the  nozzle. 
000 


And,     J7-8537  =  3.1  ins.  the  diameter. 


608  HANDBOOK    OX    KXGIXKKRINC}. 

To  find  the  approximate  size  of  suction  pipe  when  its  length 
does  not  exceed  25  ft.  and  when  there  are  not  more  than  two 
elbows  in  the  same  :  — 

Rule.  —  Square  the  diameter  of  water  cylinder  in  inches  and 
multiply  it  by  the  speed  of  the  piston  feet  in  per  minute  ;  divide 
this  product  by  200,  and  divide  this  quotient  by  .7854  and 
extract  the  square  root,  and  the  result  will  be  the  diameter  of 
suction  pipe,  except  for  very  small  pipes  when  it  should  be  made 
larger  than  the  size  given  by  the  rule,  in  order  to  lessen  the  friction 
of  the  moving  water. 

Example*  —  The  diameter  of  water  cylinder  is  6  ins.,  the  stroke 
of  piston  is  12  ins.,  and  the  number  of  strokes  per  miuute  is  60, 
what  should  be  the  diameter  of  suction  pipe?  Ans.  4  ins. 

n  6X0X60 

Operation  :  r-  —      — 


And,    1Q>8  ==  13.75. 
'  .7854 


Then,  ^/13.75  =  3.7  ins.  There  is  no  pipe  of  this  size  made, 
so  take  4-inch  pipe. 

To  find  the  velocity  in  feet  per  minute  necessary  to  discharge 
a  given  number  of  gallons  of  water  per  minute  through  a  straight 
smooth  iron  pipe  of  a  given  diameter,  regardless  of  friction  :  — 

Rule*  —  Reduce  the  gallons  to  cubic  feet  and  multiply  by  144, 
and  divide  the  product  by  the  area  of  the  pipe  in  square  inches. 

Example*  —  What  should  be  the  velocity  of  the  water  to  dis- 
charge 100  gallons  of  water  per  minute  through  a  4-inch  pipe? 

Ans.    149  ft.  per  minute. 

^  100X231 

Operation  :  •—  :  —  ^—   —  —  lo  cubic  feet. 
1728 

And,  13  X  144  =±±  1872  cubic  inches  placed  in  a  continuous 
line. 

Then,  4  X  4  X  .7854  ='=  12.5664  square  inches,  the  area  of 
pipe. 


And,   -  = 

12.5664 


HANDHOOK    ON    KMJINKKRING.  609 

To  find  the  velocity  in  feet  per  minute  of  water  flowing  through 
a  pipe  of  given  diameter,  when  the  diameter  of  water  cylinder  and 
speed  of  piston  in  feet  per  minute  are  given :  — 

Rule*  —  Multiply  the  area  of  water  cylinder  in  square  inches 
by  the  piston  speed  in  feet  per  minute,  and  divide  the  product  by 
the  area  of  the  pipe  in  square  inches. 

Example*  —  The  diameter  of  water  cylinder  is  8  ins.,  and  the 
piston  speed  is  100  ft.  per  minute,  and  the  diameter  of  discharge 
pipe  is  4  ins.,  what  is  the  velocity  of  the  water  in  the  discharge 
pipe?  Ans.  400  ft.  per  minute. 

Operation:  8  X  H  X  .7854  =  50.26  sqr.  ins.  area  of  the 
water  piston. 

And,  50.26  X  100  =  5026. 

The  area  of  the  pipe  is  12.56  sqr.  ins. 

T,,»,    «"=«». 

To  find  the  number  of  gallons  of  water  discharged  per  minute 
through  a  circular  orifice  under  a  given  head :  — 

Rule,—  Find  the  velocity  of  discharge  in  feet  per  second  and 
multiply  it  by  60,  then  multiply  this  product  by  the  area  of  the 
orifice  in  square  feet,  and  multiply  this  last  product  by  7.48,  and 
the  result  will  be  the  gallons  discharged  per  minute. 

Example. —  How  many  gallons  of  water  will  be  discharged  per 
minute  through  an  orifice  4  inches  in  diameter  under  a  head  of  81 
feet?  Ans.  2829.7  galls. 

Operation:  -^81  =  9.  And,  9  X  8.025  =  72.225  feet  per 
second,  the  velocity  of  discharge.  The  factor  8.025  is  a  con- 
stant for  any  head,  and  is  found  thusly:  - 


v'2  X32.2  ==  8.025. 

Or,  the   velocity  of  discharge  may  be  found  in  this  manner :  — 
>/2~X"32^2~x"8l  =  72.22  feet  per  second,  that  is,  the  veloc- 
ity in   feet  per  second  equals  the  square  root  of  the  acceleration 


39 


610  HANDBOOK    ON    ENGINKKKING. 

due  to  gravity  multiplied  into  the  head  in  feet.     Continuing  the 
operation,  we  have  :  — 

72.225  X  60  =  4333.5  feet  per  minute. 

And;  4  X  4  X  -7854  =  12.5664  sqr.  ins.  area  of  orifice. 

And,    — * =  .0873   of  a   square  foot,  the  area  of  orifice, 

144 

also. 

Then,  4333.5  X  -0873  =  378.3  cubic  feet. 

And,  378.3  X  7.48  =  2829.7  galls. 

NOTE.  —  With  a  ring  orifice  only  64  per  cent  of  the  above 
amount  of  water  would  be  discharged,  and  with  a  funnel-shaped 
orifice  only  82  per  cent. 

To  find  the  number  of  gallons  of  water  discharged  per  minute 
under  a  given  pressure  in  pounds  per  square  inch :  — 

Rale*  —  Divide  the  given  pressure  in  pounds  per  square  inch 
by  .433  in  order  to  get  the  head  in  feet,  and  then  proceed  accord- 
ing to  the  foregoing  rule. 

Example* —  How  many  gallons  of  water  will  be  discharged  per 
minute  through  an  orifice  one  square  inch  in  area,  under  a  pres- 
sure of  35.073  Ibs.  per  square  inch?  Ana.  81  galls,  per  minute. 

35.073 
Operation:  — 433"  =81  ft.,    head    equivalent   to   the   given 

pressure. 

And,  V2X32.2  X81  =  72.225  ft.  per  second  the  velocity. 
And,  72.225  X  60  =  4333.5. 

Also,     rjj  =  .00694  of   a  square  foot,  equals  the  area  of  the 

orifice. 

And,  4332.5  X  .00694  ==  30.07449. 

And,  30.07449  X  7.48  ==  224.9  galls. 

Then,  deducting  64  per  cent,  we  have:  — > 

224.9  X  . 64  =  143.9. 

And,  224*9  —  143.9=81.  A 


HANDBOOK    ON    ENGINEERING.  611 

To  find  the  area  of  orifice  in  square  ins.  necessary  to  discharge 
a  given  number  of  gallons  of  water  per  minute  under  a  given 
head  in  feet  :  — 

Rule.  —  Divide  the  number  of  gallons  by  the  constant  number 
15.729  multiplied  into  the  square  root  of  the  head,  and  the  result 
will  be  the  area  of  orifice  in  square  inches. 

Example*  —  What  must  be  the  area  of  orifice  to  discharge 
1778.5  gallons  of  water  per  minute  under  a  head  of  81  feet? 

Ails,    12.56  sqr.  ins. 

Operation:   V^  =  9- 


And,  9  X  15.729  =  141.6. 
1778.5 

Then'  -T4T6  =  12-56' 

To  find  how  many  gallons  of  water  will  flow  through  a  straight 
smooth  iron  pipe  in  one  minute  under  a  given  pressure  in  pounds 
per  square  inch,  or  head  in  feet  :  — 

Rule*  —  Multiply  the  inside  diameter  of  the  pipe  hi  feet  by  the 
head  in  feet,  and  divide  the  product  by  the  length  of  pipe  in  feet. 
Extract  the  square  root  of  the  quotient  and  multiply  it  by  48, 
and  the  product  will  be  the  velocity  of  flow  in  feet  per  second. 
Multiply  this  result  by  12  to  reduce  it  to  inches,  and  by  60  for 
the  flow  per  mmute,  and  multiply  again  by  the  area  of  the  pipe  in 
square  inches,  and  divide  by  231  for  the  gallons  discharged  per 
minute. 

Example*  —  How  many  gallons  of  water  will  be  discharged  per 
minute  through  a  4-inch  pipe  2000  feet  long,  under  a  head  of  92 
feet?  Ans.  230  galls,  per  minute. 

Operation  :  4  ins.  =  .33  of  a  foot. 

And,  92  X  .33  =  30.36. 

30.36 
And'     2000"  = 


612  HANDBOOK    ON    ENGINEERING. 


And,  V>5  =  .1225. 

Then,  .1225  X  48  X  12  =  70.56  ins.  per  second. 

And,  70.56  X'  60  =4233.60  ins.  per  minute. 

Then,  4  X  4  X  .7854  —  12.56  sqr.  ins.  the  area  of  the  pipe. 

And,  4233.60  X  12.56  =53174.016  cubic  ins. 

53174.016 
Then,  —      --  =  230.2. 


Example.  —  Assume  two  wells  A  and  B  with  their  mouths  on 
a  level.  Well  A  is  26  ft.  deep,  and  well  B  is  40  ft.  deep.  Well 
A  is  fed  by  natural  springs  and  has  a  depth  of  water  of  5  feet. 
The  distance  between  the  wells  is  600  feet.  How  many  gallons 
of  water  will  a  1  inch  pipe,  laid  perfectly  straight  and  level, 
syphon  over  in  one  minute  providing  well  B  is  always  pumped 
dry,  and  that  the  pipe  extends  into  well  A  26  feet,  and  into  well 
B  38  feet,  using  bends  instead  of  elbows? 

Ans.  4  galls,  per  minute. 

Operation*  —  The  head  equals  38  feet. 
The  diameter  of  the  pipe  equals  .0833  foot. 
Then,  600  -f  38  +  26  =664  ft.  total  length  ot  pipe. 
And,  38  X  .0833  =  3.1654. 

3.1654 
And>    -664- 


And,  V -0047  =  .068. 

Then,  .068  X  48  =  3.264  ft.  velocity  per  second. 
And,  3.264  X  60  =  195.840  ft.  velocity  per  min. 
The  area  of  pipe  equals  .7854  sqr.  inch. 
Then,  195.840  X  .7854  =  153.8127. 
And,   153.8127X7.48  =  1150.52. 

1150.52 
And,     ~TZi~~  —  8  nearly,  gallons. 


HANDBOOK    ON    ENGINEERING.  613 

Deducting  50  per  cent  on  account  of  2  bends  and  friction,  we 
have  4  gallons  per  minute  syphoned  over. 

To  find  the  head  in  feet  due  to  friction  in  a  pipe  running 
full  :  - 

Rule,  —  Multiply  the  length  of  the  pipe  in  feet  by  the  square 
of  the  number  of  gallons  per  minute,  and  divide  the  product  by 
1,000  times  the  5th  power  of  the  diameter  of  the  pipe  in  inches. 
The  quotient  less  10  per  cent  is  the  head  in  feet  necessary  to  over- 
come the  friction. 

NOTE.  —  The  head  is  the  vertical  distance  from  the  surface  of 
the  water  in  the  tank  or  reservoir,  -to  the  center  of  gravity  of  the 
lower  end  of  the  pipe,  when  the  discharge  is  into  the  air,  or,  to 
the  level  surface  of  the  lower  reservoir  when  the  discharge  is  under 
the  water. 

Example*  —  A  2-inch  pipe  100  feet  long  and  running  full, 
discharges  50  gallons  of  water  per  minute,  what  is  the  head  in 
feet  due  to  friction?  Ans.  7.029  feet. 

Operation  :  2  X  2  X  2  X  2  X  2  =  32  =  the  5th  power  of  the 
diameter  of  the  pipe. 

And,  50  X  50  =  2500. 
And,  2500  X  100  =  250,000. 
Also,  32  X  1,000  =  32,000. 
250,000 

Then> 


And,  7.81  less  10  percent  of  itself  equals  7.029. 
The  resistance  to  the  flow  of  water  in  pounds  per  square  inch, 
due  to  friction,  is  found  by  dividing  the  friction  head  by  2.3. 

7.029 
Thus,    2Q3  =3.051bs. 

To  find  the  size  of  pump  required  to  feed  a  boiler  of  a  given 
capacity  :  — 


614  HANDBOOK    ON    ENGINEERING. 

Rule.  —  Multiply  the  number  of  pounds  of  water  evaporated 
per  pound  of  coal  by  the  number  of  pounds  of  coal  burned  per 
sqr.  foot  of  grate  surface  per  hour,  and  multiply  this  product  by 
the  number  of  square  feet  of  grate  surface  in  the  boiler  furnace. 
This  will  give  the  number  of  pounds  of  water  evaporated  by  the 
boiler  in  one  hour.  Divide  this  by  60  to  find  the  evaporation  per 
minute,  and  divide  again  by  8i  in  order  to  get  the  evaporation  in 
gallons  per  minute  ;  add  from  10  to  15  per  cent  to  the  last  result 
for  leakage  and  other  contingencies,  and  select  a  pump  that  will 
deliver  the  gross  number  of  gallons  of  water  per  minute  at  any 
speed  that  may  be  desired,  usually  taken,  however,  at  100  feet 
per  minute. 

Example*  —  What  should  be  the  dimensions  of  the  water  end 
of  a  steam  pump,  and  what  should  be  the  speed  of  piston  to  sup- 
ply a  boiler  having  a  grate  surface  of  20  square  feet,  and  burning 
15  pounds  of  coal  per  square  foot  of  grate,  and  evaporating  9 
pounds  of  water  per  pound  of  coal  per  hour  ? 

Operation ;20X15X9  —  2700  pounds  of  water  evapo- 
rated per  hour. 

And,   =  45  Ibs.  of  water  evaporated  per  minute. 

60 

And,  =  5.4  galls,  per  minute. 

Then,  5.4  plus  10  per  cent  of  itself,  equals  6  galls,  nearly  per 
per  minute. 

Referring  to  a  pump  maker's  catalogue  we  find  that  a  single 
pump  3|"  X  2|"  X  5",  making  90  strokes  per  minute,  will  do 
the  work,  or,  a  duplex  pump  3"  X  2"  X  3",  making  100  strokes 
per  minute  will  do  the  work  equally  as  well.  Again,  adding  10 
per  cent  to  the  pounds  of  water  evaporated  per  minute  we  have, 
45  +  4.5  =49.5  pounds.  And,  49.5  X  27.71  =  1371.64  cubic 
inches  displacement  in  the  water  cylinder  per  minute,  and  at  90 
strokes  per  minute  we  have  15.24  cubic  inches  displacement  per 
stroke. 


HANDBOOK    OX    ENGINEERING.  615 

Thus,  —  15.24   which  is  all  that  is  required  for  our 

yo 

boiler. 

Now,  taking  the  above  single  pump  we  have:  2.25  X  2.25  X 
.7854  X  5  =  19.8  cubic  inches  displacement  per  stroke.  And, 
taking  the  duplex  pump  we  have:  2  X  2  X  .7854  X  3  X  2  = 
18.8  cubic  ins.  displacement  for  each  double  stroke  of  the  piston, 
or,  plunger,  showing  that  either  pump  is  of  ample  capacity  to 
feed  the  boiler  at  a  fair  piston  speed. 

To  find  the  duty  of  a  pumping  engine  when  the  number  of 
pounds  of  coal  burned,  the  number  of  gallons  of  water  pumped, 
the  pressure  in  pounds  per  square  inch  against  which  the  pump 
piston  works,  and  the  height  of  suction  are  given :  — 

Rule* — Find  the  head  in  feet  against  which  the  pump  works, 
by  multiplying  the  pressure  by  2.3,  add  the  suction  in  feet 
to  this  head  in  order  to  get  the  total  head.  Multiply  the 
gallons  of  water  by  8J  to  get  the  pounds  of  water  deliv- 
ered. Then  multiply  the  total  number  of  pounds  of  water 
by  the  head  in  feet,  and  divide  the  product  by  the  number  of 
pounds  of  coal  divided  by  100,  and  the  result  will  give  the  duty 
in  foot  pounds.  The  duty  of  a  pumping  engine  is  the  number  of 
pounds  of  water  raised  one  foot  high  for  each  100  pounds  of  coal 
burned. 

Example*  —  What  is  the  duty  of  an  engine  pumping  2,890,000 
gallons  of  water  in  12  hours  against  a  pressure  of  30  pounds  per 
sqr.  inch,  the  suction  being  12  feet,  and  coal  burned  24,470 
pounds?  Ans.  8,070,426  foot  pounds. 

Operation:  30  X  2.3  =  70  nearly  the  head  in  feet. 

And,  2,890,000  X  8J  =  24,083,333  pounds  of  water. 

Also,  70  -f  12  =  82  ft.  total  lift  of  water. 

And,  24,083,333  X  82  =  1,974,833,306  Ibs.  of  water  lifted 
one  foot  high  in  12  hours. 


616  HANDBOOK    ON    ENGINEERING. 

And,   M74.883.806  =  8,070,426. 

To  find  the  horse  power  of  a  pumping  engine :  — 

Rule* — Divide  the  number  of  pounds  of  water  raised  one  foot 
high  in  one  minute  by  33,000. 

Example*  —  What  is  the  H.  P.  of  the  pumping  engine  given 
in  the  above  example?  Ans.  83.11  H.  P. 

Operation:  12  X  60  =  720  minutes. 

And,   1'974'888'8QG  =  2,742,824  Ibs.  of  water  raised  one  foot 
720 

high  in  one  minute,, 

Then,   2,742,824  =  83>n> 
•    33,000 

To  find  the  capacity  of  a  pump  to  feed  a  boiler  it  is  necessary 
to  know  how  much  water  the  boiler  is  capable  of  evaporating  per 
minute  or  per  hour.  Each  horse  power  of  boiler  capacity  corre- 
sponds to  an  evaporation  of  thirty  pounds  of  water  per  hour.  It 
is  good  practice  to  operate  a  pump  slowly  and  continuously,  and 
for  this  reason  the  pump  running  at  its  normal  speed  should  be 
capable  of  supplying  about  twice  as  much  water  as  the  boiler 
evaporates  under  usual  conditions. 

To  find  the  diameter  of  water  cylinder  to  deliver  a  certain  num- 
ber of  gallons  of  water  per  minute,  when  the  stroke  of  the  piston 
and  the  number  of  strokes  per  minute  are  given :  - 

Rule.  —  Multiply  the  number  of  gallons  by  231,  and  divide  the 
product  by  the  stroke  of  the  piston,  and  divide  this  quotient  by 
the  number  of  strokes  per  minute,  and  divide  this  last  quotient 
by  .7854,  then  extract  the  square  root  of  the  result  for  the 
diameter  of  the  water  piston. 

Example*  —  A  battery  of  boilers  evaporate  100,000  pounds  of 
water  in  one  hour,  what  should  be  the  diameter  of  water  cylinder 
to  supply  this  battery,  the  stroke  of  piston  being  12  inches  and 
making  100  strokes  per  minute?  Ans.  7  inches. 


HANDBOOK    ON    ENGINEERING.  617 

100,000 
Operation: gx — =  1666|   pounds  of  water  evaporated  in 

one  minute. 

L666| 
And,     — 7rj—  =200  galls,   evaporated   in  one    minute.     Then 

following  the  above  rule  we  have :  — 
200X231       =46200. 

46200 
And,     -jg—  =  3850. 

3850 
And'  "iOO'  38'5' 

38.5 
And'  77854^ 

Then,     j/49  =  1"  the  required  diameter. 

To  determine  the  H.  P.  of  boiler  a  steam  pump  of  given 
dimensions  will  supply  when  the  number  of  strokes  per  minute 
are  given :  — 

Rule*  —  Multiply  the  area  of  the  piston  is  square  inches  by  the 
stroke  of  piston  in  inches,  and  this  product  divided  by  231  will 
give  the  gallons  per  stroke.  Multiply  this  quotient  by  the  num- 
ber of  strokes  per  minute  for  the  number  of  gallons  per  minute, 
and  by  60  for  the  number  of  gallons  per  hour.  Multiply  this 
product  by  8^  to  find  the  number  of  pounds  of  water  per  hour 
delivered  by  the  pump,  and  divide  this  product  by  30  for  the 
H.  P.  of  boiler  the  pump  will  supply.  This  rule  is  based  upon  the 
assumption  that  the  full  capacity  of  the  water  cylinder  is  deliv- 
ered at  each  stroke,  no  allowance  being  made  for  slippage,  leak- 
age, or  short  strokes. 

Example*  —  The  water  piston  of  a  steam  pump  is  6  inches  in 
diameter  and  has  a  stroke  of  12  inches,  making  100  strokes  per 
minute,  what  H.  P.  of  boiler  will  the  pump  supply? 

Ans.  2448  H.  P. 


618  HANDBOOK    ON    ENGINEERING. 

Operation:  6  X  6  X  .7854  ^28.2744  sqr.  ins.  area  of 
piston. 

And,     28.2744  X  12  =  339.2928  cubic  inches  for  one  stroke. 

339.2928 
And,      — QQ^J —     =*  1.4688  galls,  per  stroke. 

And,     1.4688  X  100  =  146.88  galls,   per  minute. 

And,     146.88  X    «0  =  8812.8  galls,  per  hour. 

And,     8812.8  X    8-i  =  73,440  pounds  of  water  per  hour. 

73440 

Then,       QA     =  2448  H.  P.  of  boilers. 
oU 

Watt  allowed  one  cubic  foot  (62£  Ibs.)  of  water  per  H.  P.  per 
hour.  Then  taking  this  allowance  instead  of  30  as  above,  we 

73440 
would  have,          -   =  1175  H.  P.  of  boilers  which  the  above  pump 

would  be  suitable  for,  and  which  could  be  run  very  slowly,  thus 
prolonging  the  life  of  the  pump. 

Even  though  a  suction  pipe  should  be  perfectly  air  tight,  a 
perfect  vacuum  cannot  be  formed  in  it,  because  water  contains 
air,  and  even  the  coldest  water  gives  off  some  vapor  tending,  to 
impair  the  vacuum .  Twenty-eight  feet  is  a  very  good  lift  for  a 
pump  taking  its  water  by  suction. 


HANDBOOK    ON    ENGINEERING. 


619 


CHAPTER      XXI. 
MECHANICAL   REFRIGERATION. 

About  the  first  thing  asked  by  persons  who  are  becoming 
interested  in  the  subject  of  refrigerating  and  ice-making  is,  "  Tell 
me  how  the  thing  is  done?  " 

Mechanical  refrigeration,  primarily,  is  produced  by  the  evapo- 
ration of  a  volatile  liquid  which  will  boil  at  low  temperature,  and 
by  means  of  a  special  apparatus  the  temperature  and  desired 
amount  of  refrigeration  is  placed  under  control  of  the  operator. 


Simplest  Apparatus 

Brine  Tank  or  Concealer  A, 


-* 


Elemental  Refrigerating  Apparatus. 
Fig.  1. 

The  simplest  form  of  refrigerating  mechanical  apparatus 
consists  of  three  principal  parts:  ^4,  an  ''evaporator,"  or,  as 
sometimes  called,  a  "  congealer,"  in  which  the  volatile  liquid  is 
vaporized ;  B,  a  combined  suction  and  compressor  pump,  which 


620 


HANDBOOK 


ENGINEERING. 


sucks,  or  properly  speaking,  "  aspirates  "  the  gas  discharged  by 
the  compressor  pumps,  and  under  the  combined  action  of  the 
pump  pressure  and  cold  condenser,  the  vapor  is  here  reconverted 
into  a  liquid,  to  be  again  used  with  congealer.  You  now  see  the 
function  of  the  compressor  pumps  and  condensers. 


PRINCIPLES  OF  OPERATION. 

The  action  of  all  refrigerating  machines  depends  upon  well- 
defined  natural  laws  that  govern  in  all  cases,  no  matter  what  type 
of  apparatus  or  machine  is  used,  the  principle  being  the  same  in 
all ;  while  processes  may  slightly  vary,  the  properties  of  the  par- 
ticular agent  and  manner  of  its  use  affecting,  of  course,  the 
efficiency  or  economic  results  obtained. 


Water  Supply 

Condenser  C 


FRICK  COMPAQ  Yg 

1  ENGINEERS 


Compression 

Refrigerating 

Apparatus 

Three  Parts 


UU  LI  U  U  UJU 

EXPANSION^- 

Brine  Tank  or  Congealer  A. 


Fig.  2. — Outline  drawing  of  mechanical  compression  system 

OPERATION   OF   APPARATUS. 

(See  Fig*  2*)  The  apparatus  being  charged  with  a  sufficient 
quantity  of  pure  ammonia  liquid,  which  we  will,  for  simplicity, 
assume  to  be  stored  in  the  lower  part  of  the  condenser  C',  a  small 
cock  or  expansion  valve  controlling  a  pipe  leading  to  the  congealer 


HANDBOOK    ON    KNCJ1NKKUING. 

or  brine  t:mk  J,  is  slightly  opened,  thus  allowing  tlxe  liquid  to 
pass  in  the  same  oitice  as  a  tube  or  flue  in  strain  boiler  :md  having 
precisely  the  same  function,  it  may  be  called  heating  or 
steam-making  service.  The  amount  of  water  capable  of  being 
boiled  into  steam  in  a  boiler  depends  upon  the  square  feet  of  heat- 
ing surface,  temperature  of  lire  and  pressure  of  steam ;  and 
the  same  is  true  of  the  capacity  of  heating  surface  pre- 
sented by  the  coils  in  the  evaporator.  The  heat  is  transmitted 
through  the  coils  from  surrounding  substance  to  the  ammonia 
liquid,  which  is  boiled  into  a  vapor  the  same  as  water  is  boiled 
into  steam  in  a  steam  boiler;  as  previously  explained,  the  heat 
thus  becomes  cooler ;  the  amount  taken  up  and  made  negative 
being  in  proportion  to  the  pounds  of  liquid  ammonia  evaporated. 

FUNCTION  OF  THE  RUHR  AND  CONDENSER. 

The  office  of  the  compressor,  pump  and  condenser  is  to  re- 
convert the  gas  after  evaporation  into  a  liquid,  and  make  the 
original  charge  of  ammonia  available  for  use  in  the  same  -appa- 
ratus, over  and  over  again.  It  will  appear  to  the  reader,  after 
having  carefully  followed  the  text,  that  the  pump  and  condenser 
might  be  dispensed  with,  but  these  conditions  may  only  be  eco- 
nomically realized  when  the,  at  present,  expensive  ammonia 
liquid  can  be  obtained  in  great  quantities  and  at  less  cost  than 
the  process  of  reconverting  the  vapor  into  a  liquid  by  compression 
machinery  and  condenser  on  the  spot. 

WHAT  DOES  THE  WORK. 

The  real  index  of  the  amount  of  cooling  work  possible  is  the 
number  of  pounds  of  ammonia  evaporated  between  the  observed 
range  of  temperature.  To  make  the  above  clear,  we  will  add 
that  each  pound  of  ammonia  during  evaporation  is  capable  of 
storing  up  a  certain  quantity  of  heat,  and  that  the  simplest  forms 


622  HANDBOOK    ON    ENGINEERING. 

of  refrigerating  apparatus  might  consist,  as  shown  by  engraving, 
of  two  parts,  to  wit :  A  congealer  and  a  tank  of  ammonia.  In  this 
apparatus  the  ammonia  is  allowed  to  escape  from  the  tank  into 
the  congealer  as  fast  as  the  coils  therein  are  capable  of  evapo- 
rating the  liquid  into  a  gas.  When  completely  evaporated  the 
resulting  vapor  is  allowed  to  escape  into  the  atmosphere,  which 
means  it  is  wasted,  the  supply  being  maintained  by  furnishing 
fresh  tanks  of  ammonia  as  fast  as  contents  are  exhausted.  This 
process,  while  simple,  would  be  tremendously  expensive,  costing 
at  the  rate  of  about  $200  per  ton,  refrigerating  or  ice-mel ting- 
capacity.  To  recover  this  gas  and  reconvert  to  a  liquid  on  the 
spot  in  a  comparatively  inexpensive  manner,  is  the  object  to  be 
obtained. 

MECHANICAL  COLD  EASILY  REGULATED. 

This  being  under  the  control  of  the  cock  or  valve  leading  from 
the  condenser  (called  an  expansion  valve).  As  the  gas  begins  to 
form  in  the  evaporator,  the  compressor  pump  B  is  set  in  motion 
at  such  a  speed  as  to  carry  away  the  gas  as  fast  as  formed,  which 
is  discharged  into  the  condenser  under  such  pressure  as  will  bring- 
about  a  condensation  and  restore  the  gas  to  the  liquid  state ;  the 
operation  being  continuous  so  long  as  the  machinery  is  kept  in 
motion. 

UTILIZING   THE    COLD. 

To  utilize  the  cold  thus  produced  for  refrigerating,  two  meth- 
ods are  in  use,  the  first  of  which  is  called  the  brine  system ;  the 
second  is  known  to  the  trade  as  the  direct  expansion  system,  both 
of  which  I  will  now  proceed  to  explain  at  some  length. 

BRINE    SYSTEM. 

In  this  method,  the  ammonia  evaporating  coils  are  placed  in  a 
tank  which  is  filled  with  strong  brine  made  of  salt,  which  is  well 
known  not  to  freeze  at  temperature  as  low  as  zero.  This  is  the  brine 


HANDBOOK    ON    ENGINEERING.  623 

tank  or  cougealer  A.  The  evaporating  or  expansion  of  the  ammo- 
nia in  these  coils  robs  the  brine  of  heat,  as  heretofore  explained, 
the  process  of  storing  cold  in  the  brine  going  on  continuously  and 
being  regulated,  as  required,  at  the  gas  expansion  valve.  To 
practically  apply  the  cold  thus  manufactured,  the  chilled  brine  or 
non-freezing  liquid  is  circulated  by  means  of  a  pump  through 
coils  of  pipe  which  are  placed  on  the  ceilings  or  sides  of  the  apart- 
ments to  be  refrigerated,  the  process  being  analogous  to  heating 
rooms  by  steam. 

THE  BRINE  COOLS  THE  ROOMS. 

The  cold  brine  in  its  circuit  along  the  pipes  becomes  warmer 
by  reason  of  taking  up  the  heat  of  the  rooms,  and  is  finally 
returned  to  the  brine  tank,  where  it  is  again  cooled  by  the  ammo- 
nia coils,  the  operation,  of  course,  being  a  continuous  one. 

DIRECT  EXPANSION  SYSTEM. 

By  this  method,  the  expansion  or  evaporating  coils  are  not  put 
in  brine  tanks,  but  are  placed  in  the  room  to  be  refrigerated,  and 
the  ammonia  is  evaporated  in  the  coils  by  coming  in  direct  con- 
tact with  the  air  in  the  room  to  be  refrigerated,  no  evaporating 
tank  being  used. 

RATING   OF  THE   MACHINE    IN   TONS   CAPACITY. 

For  the  information  of  the  unskilled  reader,  1  will  state  that 
machines  are  susceptible  of  two  ratings ;  that  is,  either  their 
capacity  is  given  in  tons  of  ice  they  will  produce  in  one  day  (24 
hours),  called  ice-making  capacity  ;  or  they  are  rated  equal  to  the 
cooling  work  done  by  one  ton  of  ice-making  per  day  (24  hours), 
called  .refrigerating  capacity. 

DIFFERENCE   IN   THESE   RATINGS. 

Ordinarily  the  ice-making  capacity  is  taken  at  about  one-half 
of  the  refrigerating  capacity,  but  this  is  only  approximate,  and 


624 


HANDBOOK    ON    ENGINEERING. 


the  tons  of  ice  a  refrigerating  machine  will  make  depend  upon  the 
initial  temperature  of  the  water  to  be  frozen. 

UNIT  OF  CAPACITY. 

The  unit  of  capacity  is  one  ton  of  ice  made  from  water  at  o2° 
Fahr.,  into  ice  at  32°,  per  day,  which  is  equal  to  284,000  Ibs.  of 
water  cooled  one  degree,  or  284,000  heat  units,  and  is  the  tonnage 
basis  for  refrigerating  capacity  as  well  as  ice  made  from  water 
at  32°. 

THE  PREPARATION  OF  BRINE. 


Fig.  1. 

There  are  two  methods  in  general  use,  which  I  will  explain. 
Fig.  1  shows  one  of  the  methods,  which  consists  of  allowing 
water  to  percolate  through  a  body  of  salt. 

Take  a  large  water-tight  barrel  or  cask,  and  tit  a  false  bottom 


HANDBOOK    ON    ENGINEERING. 

or  wooden  grating  six  or  eight  inches  above  the  bottom  ;  this  can 
be  made  of  strips  of  wood  about  an  inch  square,  and  placed  not 
over  one-half  inch  apart.  This  false  bottom  should  be  supported 
by  two  strips  of  boards,  each  six  inches  in  width,  placed  on  edge 
and  nailed  to  the  bottom.  These  boards  should  have  several  holes 
bored  near  their  bottoms  to  permit  a  free  passage  of  water.  The 
water  inlet  should  be  below  the  false  bottom.  A  single  thickness 
of  burlap  should  be  stretched  across  the  top  of  the  false  bottom 
and  tacked  to  sides  of  barrel.  The  outlet  pipe  for  the  brine 
should  be  four  or  five  inches  below  the  top  of  the  barrel.  The 
water  is  supplied  at  the  bottom  from  a  convenient  hose  or  faucet. 
The  supply  pipe  should  be  of  about  1J  in.  diameter ;  and  the 
outlet  pipe  about  1J  in.  diameter.  If  it  is  necessary  to  make 
brine  faster  than  can  be  accomplished  with  one  barrel,  lit  up  two 
or  more  extra  barrels.  To  make  brine,  fill  the  barrel  above  the 
false  bottom  with  salt  and  turn  on  the  water.  The  salt  dissolves 
rapidly  and  more  must  be  shoveled  in  on  top.  The  barrel  must 
be  kept  full  of  salt  or  the  brine  will  not  be  of  full  strength.  No 
stirring  is  necessary.  Keep  skimming  off  all  waste  matter  rising 
to  the  top.  The  brine  outlet  should  be  provided  with  a  strainer 
of  some  kind  to  prevent  chips,  etc.,  from  running  out  with  the 
brine.  Brine  should  not  be  made  any  stronger  than  is  necessary 
to  prevent  it  from  freezing. 

Fig.  2  is  the  other  method  of  brine-making.  This  method  is 
a  water-tight  box,  say  four  feet  wide,  8  feet  long  and  2  feet  high, 
with  perforated  false  bottom  and  compartment  at  end.  Locate 
the  brine-maker  at  a  point  above  the  brine  tank.C  onmct  the 
space  under  the  false  bottom  with  your  water  supply,  extending 
the  pipe  lengthwise  of  the  box,  being  perforated  at  each  side  to 
insure  an  equal  distribution  of  water  over  the  entire  bottom  surface  ; 
use  a  valve  in  water  supply  pipe.  Near  the  top  of  the  brine- 
maker,  at  end  compartment,  put  in  an  overflow  with  large  strainer 
to  keep  back  the  dirt  and  salt,  and  connect  with  this  a  pipe,  say  three 

40 


626 


HANDBOOK    ON    ENGINEERING. 


inches  in  diameter,  with  salt  catcher  at  bottom,  leading  into  the 
brine  tank.  Use  a  hoe  or  shovel  to  stir  the  contents.  When  all  is 
ready,  partly  fill  the  box  with  water,  dump  the  salt  from  the  bags 

Salt  Gauge 


Complete  Brine  Mixing  Arrangement 
Fig.  2. 

on  the  floor  alongside  and  shovel  into  brine-maker  or  dump  direct 
from  the  bags  into  the  brine-maker  as  fast  as  it  will  dis- 
solve. Regulate  the  water  supply  to  always  insure  the  brine 
being  of  the  right  strength  as  it  runs  into  the  brine  tank.  This 
point  must  be  carefully  noticed.  Filling  the  brine  tank  with 
water  and  attempting  to  dissolve  the  salt  water  directly  therein  is 
not  satisfactory,  as  quantities  of  salt  settle  on  the  tank  bottom 
coils,  forming  a  hard  cake.  It  is  a  good  plan,  when  desired  to 
strengthen  the  brine,  to  suspend  bags  of  salt  in  the  tank,  the  salt 
dissolving  from  the  bags  as  fast  as  required ;  or  the  return  brine 
from  the  pumps  may  be  allowed  to  circulate  through  the  brine- 
maker,  keeping  same  supplied  with  salt. 

INSULATION  OF    BUILDINGS. 

The    insulation  of    buildings    used  for   the    preservation    and 
storage  of  substances  subjected  to  mechanical  refrigeration,  is  a 


HANDBOOK    ON    ENGINEERING 


627 


INSULATING  BUILDINGS  AND  COLD  STORAGE  ROOHS. 


No  1 


14.  inch  Brick 
,  4    "     Air  Space 
,9    "     Brick 
Cement  Wash 
•Pitched 
-2"x  3"Studding 
Tar  Paper 
-TT&G.  Board 
2*x  4"Studding 
-1''f&.  G.  Board 

— -Tar-Paper 

~- TT&'G.  Board 


14  Brick 
4"  Pitch  &.-Ashea 
— -.4"'  Brick 
4" Air  Space 
14"  Brick 


No  2 


36"  Brick  Wall 
Pitch 

fSheathing 
Air  Space 
2"x  4"Studding 
T'Sheathing  • 
Mineral  Wool 
2"x  4"Studding 
•1"Sheathing 


No  3 


Various  Aooroved  Methods, 


628  HANDBOOK    ON    ENGINEERING. 

matter  of  vital  importance,  when  viewed  from  an  economic  stand- 
point. It  is  true  that  by  employment  of  a  large  surplus  of 
refrigerating-  power,  poor  insulation  with  its  entailed  great  loss 
of  negative  heat  is  wastefully  overcome,  and  a  certain  amount  of 
cooling  work  can  be  accomplished ;  but  this  is  t\  bad  way  to  reach 
a  result ;  it  is  like  pumping  out  a  leaky  ship  and  keeping  ever- 
lastingly at  it,  when  the  best  way  is  to  stop  the  leak  and  be  done 
with  the  pumping  —  it  is  a  preventable  loss.  Poor  insulation  is 
like  paying  interest  on  borrowed  capital,  which  is  earning  nothing 
for  the  borrower,  a  never-ceasing  and  useless  drain  upon  the 
machinery  and  pocket-book  of  the  user. 

PERFECT   INSULATION. 

Perfect  insulation  is  when  there  is  absolutely  no  transfer  of 
heat  through  the  walls  of  a  building ;  but  this  is  scarcely  pos- 
sible. If  it  were,  once  cooling  of  the  contents  of  a  room  would 
suffice ;  for  there  being  no  loss,  they  would  continue  at  the  same 
temperature  for  an  indefinite  period.  If  all  articles  placed  in  the 
room  thereafter  were  previously  cooled  to  the  temperature  of  the 
room  before  placing  therein,  no  work  need  be  done  thereafter  in 
the  room  itself.  A  large  percentage  of  the  actual  work  of  a 
refrigerating  machine  is  required  to  make  up  for  transfer  of  heat 
through  the  walls,  floors  and  ceilings  occasioned  by  improper 
insulation,  and  the  amount  may  be  experimentally  determined 
by  proper  instruments.  Owing  to  difference  in  construction, 
exposure  and  insulation  of  building,  you  will  find  a  great  dif- 
ference in  economy  of  performance  and  work  done  by  the 
same  machine  in  use  by  different  parties  in  the  same  line  of 
business ;  and  what  a  given  machine  and  apparatus  will  do  in 
one  place  is  no  certain  guide  for  another  place  somewhat  sim- 
ilar;  the  insulation,  exposure,  and  method  of  handling  the 
business  are  mainly  responsible  for  the  difference. 


HANDBOOK    ON    ENGINEERING. 


629 


As  shown  by  the  engraving,  screw  into  the  ammonia  flask  a 
piece  of  bent  one-quarter  inch  pipe,  which  will  allow  a  small  bot- 
tle to  be  placed  so  as  to  receive  the  discharge  from  it.  This  test 
bottle  should  be  of  thin  glass  with  wide  neck,  so  that  quarter-inch 
pipe  can  pass  readily  into  it,  and  of  about  200  centimeters  capac- 
ity. Put  the  wrench  on  the  valve  and  tap  it  gently  with  a  ham- 
mer. Fill  the  bottle  about  one-third  full  and  throw  sample  out 
in  order  to  purge  valve,  pipe  and  bottle.  Quickly  wipe  off  mois- 
ture that  has  accumulated  on  the  pipe,  replace  the  bottle  and  open 


Testing  for  Water  by  Evaporation. 

valve  gently,  filling  the  bottle  about  half  full.  This  last  operation 
should  not  occupy  more  than  one  minute.  Remove  the  bottle  at 
once  and  insert  in  its  neck  a  stopper  with  a  vent  hole  for  the 
escape  of  the  gas*.  A  rubber  stopper  with  a  glass  tube  in  it  is 
the  best,  but  a  rough  wooden  stopper,  loosely  put  in,  will  answer 
the  purpose.  Procure  a  piece  of  solid  iron  that  should  weigh  not 
less  than  eight  or  ten  pounds,  pour  a  little  water  on  this  and  place 
the  bottle  on  the  wet  place.  The  ammonia  will  at  once  begin  to 
boil,  and  in  warm  weather  will  soon  evaporate.  If  any  residuum, 
pour  it  out  gently,  counting  the  drops  carefully.  Eighteen  drops 
are  about  equal  to  one  cubic  centimeter,  and  if  the  sample  taken 


630 


HANDBOOK    ON    ENGINEERING. 


amounted  to  100  cubic  centimeters,  you  can  readily  approximate 
the  percentage  of  the  liquid  remaining. 


Sectional  View  of  lo-ton  Refrigerating  Machine,  regular  pat- 
tern .    Frick  Company 's  Eclipse  Refrigerating  Machine, 
with  Placer  Slide-Valve  Throttling  Machine. 


LUBRICATION   OF   REFRIGERATING   MACHINERY. 

It  is  well  to  speak  of  this,  for  the  reason  that  it  is  an  important 
subject ;   and  some  users  of  machinery  think  that  a  cheap,  low 

29 


HANDBOOK    ON    ENGINEERING.  631 

grade  of  oil  is  really  the  cheapest.  To  disabuse  their  minds  of 
this  idea  and  suggest  the  necessity  of  high  grade  oils,  both  on  the 
score  of  economy  and  to  keep  the  machinery  at  all  times  in 
efficient  running  order,  is  the  object  of  this  article.  First-class 
refrigerating  machinery  calls  for  the  use  of  at  least  three- different 
kinds  of  oil,  Nos.  1,  2  and  3,  each  of  high  grade:  — 

No*  f.  For  use  in  the  steam  cylinder,  and  is  known  in  the  trade 
as  cylinder  oil.  This  ranges  in  price  from  50c.  to  $1  per  gallon. 
Good  cylinder  oil  should  be  free  from  grit,  not  gum  up  the  valves 
and  cylinder,  should  not  evaporate  quickly  on  being  subjected  to 
heat  of  the  steam,  and  when  cylinder  head  is  removed,  a  good 
test  is  to  notice  the  appearance  of  the  wearing  surfaces ;  they 
should  be  well  coated  with  lubricant  which,  upon  application  of 
clean  waste,  will  not  show  a  gummy  deposit  or  blacken.  Use  this 
oil  in  a  sight  feed  lubricator  with  regular  feed,  drop  by  drop. 

No*  2*  For  use  of  all  bearing  and  wearing  surfaces  of  machine 
proper  —  an  oil  that  will  not  gum,  not  too  limpid,  with  good 
body,  free  from  grit  or  acid  and  of  good  wearing  quality,  flowing 
freely  from  the  oil  cups  at  a  fine  adjustment  without  clogging, 
and  a  heavier  grade  should  be  used  for  lubricating  the  larger 
bearings. 

No.  3*  For  use  in  compressor  pumps.  This  oil  should  be  what 
is  called  a  cold  test,  or  zero  oil,  of  best  quality. 

Best  paraffine  oil  is  sometimes  used ;  as  also  a  clear  West  Vir- 
ginia crude  oil.  This  oil,  when  subjected  to  a  low  temperature, 
should  not  freeze. 

EFFECTS  OF  AMMONIA  ON  PIPES. 

Ammonia  has  no  chemical  effect  upon  iron ;  a  tank,  pipe  or 
stop-cock  may  be  in  constant  contact  with  ammonia  for  an  in- 
definite time  and  no  action  will  be  apparent.  The  only  protec- 
tion, therefore,  that  ammonia-expanding  pipes  require  is  from 
corrosion  on  the  outer  surface.  As  long  as  the  pipes  are  covered 


632 


HANDBOOK    ON    ENGINEERING. 


with  snow  or  ice,  corrosion  does  not  occur ;  the  coating  of  ice 
thoroughly  protects  them  from  the  oxidizing  effect  of  the  atmos- 
phere ;  but  alternate  freezing  and  thawing  requires  protected  sur- 
faces, which  are  best  obtained  by  applying  a  coat  of  paint  every 
season . 

Expansion  coils  having  to  Withstand  but  a  maximum  working 
pressure  of  thirty  pounds  per  square  inch,  are  constructed  with 
such  absolute  security,  in  whole  and  in  detail,  as  to  make  them 
one  of  the  most  perfect  pipe  constructions  on  a  large  scale  ever 
applied  in  practice. 


POSITION  OF  TANK  TO  BE  EMPTIED.. 


TO  CHARGE  THE  SYSTEM  WITH  AMMONIA. 

Position  of  the  tank  should  be  as  shown,  the  outlet  valve 
pointing  upwards  and  the  other  end  of  the  tank  raised  12"  to  15". 
The  connection  between  the  outlet  valve  of  the  tank  and  the 
inlet  cock  of  the  system  should  be  a  |"  pipe.  In  charging,  open 
valve  of  the  tank  cautiously  to  test  connection  ;  if  this  is  tight, 
open  valve  fully;  start  machine  and  run  slowly  till  tank  is  empty. 
The  tank  is  nearly  empty  when  frost  begins  to  appear  on  it ;  run 
the  machine  till  suction  gauge  reaches  atmospheric  pressure.  If 
it  holds  at  this  pressure  when  machine  is  stopped,  the  tank  is 
empty;  if  not,  start  up  again.  In  disconnecting,  close  the  valve 
on  the  tank  first,  the  inlet  cock  of  the  system.  Weigh  tank 


HANDBOOK    OX    ENGINEERING. 


633 


before  and  after  emptying ;   each  standard  tank  contains  from  100 
to  110  pounds  of  ammonia. 

PROCESS  OF  MECHANICAL  REFRIGERATION. 

The  process  of  mechanical  refrigeration  is  simply  that  of 
removing  heat,  and  mechanism  is  necessary,  because  the  rooms 
and  articles  from  which  the  heat  is  to  be  removed  are  already  as 
cold,  or  colder  than  their  surroundings,  and  consequently,  the 
natural  tendency  is  for  the  heat  to  flow  into  them  instead  of  out  of 
them.  The  fact  that  a  body  is  already  cold  does  not  prevent  the 
removal  of  more  heat  from  it  and  making  it  still  colder.  The  term 
cold  describes  a  sensation  and  not  a  physical  property  of  matter ; 
the  coldest  bodies  we  commonly  meet  with  are  still  possessed  of  a 
large  quantity  of  heat,  part  of  which,  at  least,  can  be  abstracted 
by  suitable  means.  The  only  means  by  which  heat  can  be 
removed  from  a  body  is  to  bring  in  contact  with  it  a  body  colder 
than  itself.  This  is  the  function  that  ammonia  performs  in 
mechanical  refrigeration.  It  is  so  manipulated  as  to  become 
colder  than  the  body  we  wish  to  cool.  The  heat  thus  abstracted 
by  it  is  got  rid  of  by  such  further  manipulation  that  (while  still 
retaining  the  heat  it  has  absorbed)  it  will  be  hotter  than  ordi- 
nary cold  water,  and  therefore,  part  with  its  heat  to  it.  Ammonia 
thus  acts  like  a  sponge.  It  sops  up  the  heat  in  one  place  and 
parts  with  it  in  another,  the  same  ammonia  constantly  going 
backward  and  forward  to  fetch  and  discharge  more  heat.  The 
complete  cycle  of  operation  comprises  three  parts :  — 

1st.  A  compression  side ,  in  which  the  gas  is  compressed. 

2d.  A  t'OH<lc.ming  side,  generally  consisting  of  coils  of  pipe, 
in  which  the  compressed  gas  circulates,  parts  with  its  heat  and 
liquefies. 

3d.  An  expansion  side,  consisting  also  of  coils  of  pipe, 
in  which  the  liquefied  gas  re-expands  into  a  gas,  absorbs  heat, 
and  performs  the  refrigerating  work. 


t)34  HANDBOOK    ON    ENGINEERING. 

In  order  to  render  the  operating  continuous,  these  three  sides 
or  parts  are  connected  together,  the  gas  passing  through  them  in 
the  order  named.  The  liquefied  gas  is  allowed  to  flow  into  the 
expansion  or  evaporating  coils,  where  it  vaporizes  and  expands 
under  a  pressure  varying  from  10  to  30  pounds  above  that  of  the 
atmosphere,  when  ammonia  is  the  agent  in  use.  The  gas  then 
passes  into  the  compressor,  is  compressed  and  forced  into  the 
condensers,  where  a  pressure  from  125  to  175  pounds  per  square 
inch  usually  exists ;  here  liquefaction  takes  place  and  the  re- 
sulting liquefied  gas  is  allowed  to  flow  to  a  stop-cock  having  a 
minute  opening,  which  separates  the  compression  from  the  expan- 
sion side  of  the  plant.  The  expansion  side  consists  of  coils  of 
pipe  similar  to  those  of  the  condensing  side,  but  used  for  the 
reverse  operation,  which  is  the  absorption  of  heat  by  the  vapor- 
ization of  liquefied  gas  instead  of  the  expulsion  of  heat  from  it, 
as  in  the  former  operation.  Heat  is  conducted  through  the  ex- 
pansion or  cooling  coils  to,  and  is  absorbed  by,  the  vaporizing 
and  expanding  liquefied  gas  within  such  coils,  for  the  reason  that 
they  are  connected  to  the  suction  or  low  pressure  side  of  the 
apparatus  from  which  the  compressors  are  continually  drawing 
the  gas  and  thereby  reducing  the  pressure  in  said  coils,  as  already 
stated,  to  a  pressure  of  10  to  30  pounds  above  the  atmosphere; 
it  being  kept  in  mind  that  liquefied  ammonia  in  again  assuming 
a  gaseous  condition,  has  the  power  or  capacity  of  reabsorbing, 
upon  its  expansion,  a  large  quantity  of  heat.  The  liquefied  gas 
entering  these  coils  through  the  minute  openings  of  the  stop-cock, 
above  referred  to,  is  relieved  of  a  pressure  of  125  to  175  pounds, 
the  amount  requisite  to  maintain  it  in  a  liquid  condition,  when  it 
begins  to  boil,  and  in  so  doing  passes  into  the  gaseous  state.  To 
do  this  it  must  have  heat,  which  can  be  supplied  only  from  the 
substance  surrounding  the  pipes,  such  as  air,  brine,  wort,  etc. 
As  a  natural  result  the  surrounding  substances  are  reduced  in 
temperature,  or  cooled.  It  is  apparent  from  the  foregoing  that 


HANDBOOK    OX    ENGINEERING. 


635 


The  above  is  a  Sectional  Cut  of  the  "Eclipse"  Compressor. 


636  HANDBOOK    ON    ENGINEERING. 

if  the  expansion  coils  are  placed  in  an  insulated  room,  that  room 
will  be  refrigerated ;  also,  if  brine  or  wort  is  brought  in  contact 
with  the  surface  of  the  coils,  they  also  will  be  reduced  in  tem- 
perature ;  and  that  brine  so  cooled  can  be  used  to  refrigerate  an 
insulated  room  by  simply  forcing  it  to  circulate  through  pipes 
or  gutters  suspended  in  the  same.  Either  of  the  above  methods 
can  be  applied  to  the  refrigeration  of  breweries,  packing-houses, 
etc.,  and  for  the  manufacture  of  ice,  the  same  gas  being  used 
over  and  over  again  to  perform  the  same  cycle  of  operations. 

THE  COMPRESSOR  PUMPS. 

The  most  important  feature  of  a  refrigerating  machine  is  the 
compressor  pump.  To  some,  the  highest  efficiency  of  perform- 
ance (other  things  being  equal,  such  as  proper  application  and 
proportion  of  the  steam  engine  dividing  the  same,  with  the  lowest 
obtainable  loss  of  friction  in  transmission  of  power  to  the 
pump)  is  the  pump  which  receives  the  fullest  charge  of  gas 
and  most  perfectly  expels  the  same ;  this  is  the  most  efficient 
and  will  do  the  most  work. 

THE  DE  LA  VERQNE  HORIZONTAL  COMPRESSOR. 

This  compressor  is  of  an  entirely  new  design,  embodying  all 
the  improvements  suggested  by  experience  up  to  date,  and  having, 
moreover,  many  original  features. 

Particular  attention  is  directed  to  the  following  points :  — 

The  valves  are  all  in  the  body  of  the  compressor. 

No  pipe  joints  have  to  be  broken  to  remove  the  valves  or  the 
cages. 

The  delivery  valves  are  so  placed  as  to  allow  a  free  and  early 
draining  of  the  cylinder,  if  liquid  should  be  present. 

The  valves  tux*   so   arranged  and  provided  with   such  safety 


HANDBOOK    ON    ENGINKKKI  N< ! . 


637 


devices  as  to  render  it  impossible  for  them  to  get  inside  the  cylin- 
der under  any  circumstances. 

The    stuffing-box    's    effectually    sealed,    without    producing 
undue  friction. 


PIPE  ARRANGEMENT  FOR  VAULTS. 
Showing  method  of  supporting,  Jrom  Ceiling. 


Flat  Pipe  Coils  Suspended  from  Ceiling  on  Iron  Floors — Beams 
for  Storage  and  Fermenting  Rooms. 


DIAGRAM  OF  DE  LA  VERQNE  SYSTEM. 

The  diagram  on  page  638  is  seen  to  be  extremely  simple  in 
conception  ;  ammonia,  gas  and  oil  are   received   into  the   com- 

^ 


638 


HANDBOOK    ON    ENGINEERING. 


pressor,  from  which  they  are  discharged  together  into  the  cooler. 
The  cooled  oil  drops  into  the  first  tank  while  the  gas  continues 
into  the  condenser,  where  it  is  liquefied  and  collects  in  the  second 
tank.  The  liquid  ammonia  is  taken  off  from  a  point  near  the  top 
of  the  second  tank.  If  a  little  oil  is  taken  over  from  the  conden- 
ser it  is  conveyed  by  a  pipe,  as  shown,  to  a  point  near  the  bottom 


COOLING  WATER. 


OIL  COOLER. 


— m- 


COOLING  WATER. 


CONDENSER. 


OIL  RETURN  PIPE. 


OIL  RETURN  PIPE. 


EXPANSION    COIL. 


EXPANSION 
COCK. 


of  the  second  tank,  where  it  remains,  since  it  is  heavier  than 
liquid  ammonia,  and  cannot  rise  to  get  into  the  liquid  pipe  of  the 
ammonia  supply.  The  liquid  ammonia  is  passed  through  the 
expansion  cock  into  the  expansion  coil,  where  it  boils  into  vapor 
which  is  drawn  off  into  the  compressor  to  pass  around  again  in 
the  order  above  described. 


RATING  MACHINES  FOR  ICE-flAKING. 


Refrigerating  machines  are  rated  by  the  effect  they  produce 
equivalent  to  the  melting  of  a  corresponding  amount  of  ice.  Now 
the  melting  of  one  pound  of  ice  is  equivalent  to  the  absorbing  of 


HANDBOOK    OX    ENGINEERING. 


639 


I 
o 


8 


640 


HAND  BOOK    O  N     K  NCI  X  E  FIRING . 


o 
s- 

OQ 
K 


HANDBOOK    ON    ENGINEERING. 


641 


142  units  of  heat.  In  making  ice  from  water,  we  have,  however, 
to  remove  more  than  142  units.  We  have  first  of  all  to  reduce 
the  water  to  32°  before  we  are  ready  to  produce  ice.  If  the  water 
is  at  82°  this  means  the  removal  50  heat  units.  Moreover,  we 
cannot  make  ice  with  economy  without  going  to  a  temperature 
much  lower  than  32°.  The  ice  when  formed  may  have  a  temper- 
ature of  18°,  and  the  specific  heat  of  ice  being  0.5  this  means  the 


THE  DE  L*  VeRONE  IcE-M*KINO  SYSTEM. 

The  above  cut  shows,  in  diagrammatic  form ,  the  general  outline  of 
the  process  of  ice-making  with  cans, 

removal  of  7  more  heat  units.  In  other  words,  we  have  to 
remove  199  heat  units  instead  of  142  to  produce  a  Ib.  of  ice. 
Thus  a  200-ton  machine  which  would  easily  produce  a  refrigerat- 
ing effect  equal  to  the  melting  of  200  tons  of  ice  would  only  pro- 
duce 142  tons  of  actual  ice.  This  proportion  is  still  further 
reduced  by  the  inevitable  losses  attending  the  use  of  large  freezing 
tanks  and  the  handling  of  the  ice. 

41 


642 


HANDBOOK    ON 


HANDBOOK    ON    ENGINEERING.  643 

COHPLETE  CYCLE  STANDARD  DE  LA  VERGNE  VERTICAL 
MACHINE. 

The  cut  on  preceding  page  shows  the  engine-room  connections 
for  the  double  acting  vertical  compressor  complete  with  Corliss 
engine.  The  course  of  the  gas  can  be  very  readily  followed  : 
After  being  discharged  from  the  compressor  it  rises  to  the  fore 
cooler,  where  the  oil  is  cooled  and  deposited  in  the  pressure  tank. 
The  ammonia  gas  goes  on  to  the  condenser,  which  it  enters  at  the 
bottom.  As  fast  as  the  liquid  ammonia  collects  in  the  condenser, 
it  is  drawn  off  at  different  levels  in  the  manner  already  described 
in  connection  with  the  condensers.  From  the  storage  tank  it  falls 
into  the  separating  tank,  where  any  remaining  oil  is  trapped,  and 
the  anhydrous  ammonia  passes  into  the  rooms  to  be  cooled  by  way 
of  the  main  liquid  pipe. 

The  sectional  view. on  following  page,  represents  one  of  the 
J)e  La  Vergne  Double  Acting  Vertical  Compressors,  as  arranged 
for  use  with  oil,  as  a  sealing,  lubricating  and  cooling  agent.  Two 
passages,  marked  "  suction"  and"  discharge,"  respectively,  con- 
nect the  compressor  with  the  pipe  system.  On  the  up  stroke,  gas 
flows  through  the  lower  suction  valve  into  the  space  behind  the 
moving  piston,  while  the  gas  above  the  piston,  after  being  com- 
pressed to  the  condenser  pressure,  is  discharged  through  the  up- 
per valves  (in  the  loose  head)  into  the  discharge  passage.  On 
the  down  stroke,  gas  flows  into  the  cylinder  through  the  upper 
suction  valves,  and  the  gas  below  the  piston  is  compressed  and 
passes  through  the  lower  discharge  valves  into  the  discharge  pas- 
sage. The  piston  in  its  downward  course,  closes  successively  the 
openings  of  these  two  discharge  valves.  When  the  lower  is 
closed,  however,  the  upper  one  communicates  with  the  chamber 
in  the  piston,  and  the  gas  and  oil  still  remaining  below  the  piston 
are  discharged  through  the  valves  into  the  chamber  and  out  by 
the  upper  discharge  valve.  The  oil  being  injected  directly  into 


644 


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HANDBOOK    ON    ENGINEERING. 


645 


the  compressor  after  the  compression  of  the  full  cylinder  of    gas 
has  commenced,  does  not  reduce  the  capacity  of  the  machine,, 


The  above  is  a  cut  of  the  De  La  Vergue  Double  Acting  Com- 
pressor, driven  by  a  Corliss  Engine.  Both  the  compressor  and 
engine  cylinder,  affording  an  opportunity  of  observing  the  relative 
positions  of  the  pistons  in  each. 

The  oil  for  "  cooling,  sealing  and  lubricating  "  is  brought  to 
the  compressor  by  the  pipe  running  along  the  back  of  the  l '  A  " 
frame.  The  pipe  marked  "  By-pass  "  is  used  when  any  portion 
of  the  pipe  system  in  the  engine  house  is  to  be  independently 
exhausted  of  gas. 


646  HANDBOOK   ON    ENGINEERING. 


CHAPTER     XXII. 

SOflE    PRACTICAL    QUESTIONS    USUALLY    ASKED     OF     EN- 
GINEERS WHEN   APPLYING   FOR  LICENSE. 

Q.  If  you  were  called  on  to  take  charge  of  a  plant,  what  would 
be  your  first  duty  ?  A.  To  ascertain  the  exact  condition  of  the 
boiler  and  all  its  attachments  (safety-valve,  steam-gauge,  pump, 
injector)  and  engine. 

Q.  How  often  would  you  blow  off  and  clean  your  boilers  if 
you  had  ordinary  water  to  use?  A.  Twice  a  month. 

Q.  What  steam  pressure  will  be  allowed  on  a  boiler  50"  diam- 
eter, |"  thick,  60,000  T.  8.  -J  of  tensile  strength  factor  of  safety? 
A.  One-sixth  of  tensile  strength  of  plate,  multiplied  by  thick- 
ness of  plate,  divided  by  one-half  of  the  diameter  of  boiler,  gives 
safe  working  pressure. 

Q.  How  much  heating  surface  is  allowed  per  horse-power  by 
builders  of  boilers?  A.  12  to  15  feet  for  tubular  and  flue  boilers. 

Q.  How  do  you  estimate  the  strength  of  a  boiler?  A.  By  its 
diameter  and  thickness  of  metal. 

Q.  Which  is  the  best,  single  or  double  riveting?  A.  Double 
riveting  is  from  16  to  20  per  cent  stronger  than  single. 

Q.  How  much  grate  surface  do  boiler-makers  allow  per  horse- 
power? A.  About  |  of  a  square  foot. 

Q.  Of  what  use  is  a  mud  drum  on  a  boiler,  if  an}- ?  A.  Foi 
collecting  all  tlie  sediment  of  a  boiler. 

Q.  How  often  should  it  be  blown  out?  A.  Three  or  four  times 
a  day,  in  the  morning  before  starting,  and  at  noon. 

Q.  Of  what  use  is  a  steam  dome  on  a  boiler?  A.  For  storage 
of  dry  steam. 


HANDBOOK    ON    ENGINEERING.  647 

Q.  What  is  the  object  of  a  safety-valve  on  a  boiler?  A.  To 
relieve  over  pressure. 

Q.  What  is  your  duty  with  reference  to  it  ?  A.  To  raise  it  once 
a  day  and  see  that  it  is  in  good  order. 

Q.  What  is  the  use  of  a  check  valve  on  a  boiler?  A.  To  pre- 
vent the  water  from  returning  back  into  the  pump  or  injector 
which  feeds  the  boiler. 

Q.  Do  you  think  a  man-hole  in  the  shell  on  top  of  a  boiler 
weakens  it  any?  A.  Yes,  to  a  certain  extent. 

Q.  What  effect  has  cold  water  on  hot  boilerplates?  A.  It 
will  crack  or  fracture  them. 

Q.  Where  should  the  gauge  cocks  be  located?  A.  The  lowest 
gauge  cock  ought  to  be  placed  about  3  inches  above  the  top  row  of 
flues. 

Q.  How  would  you  have  your  blow-off  located  ?  A.  In  bottom 
of  mud  drum  or  boiler. 

Q.  How  would  you  have  your  check  valve  arranged?  A.  With 
a  stop  cock  between  check  and  boiler. 

Q.  How  many  vajves  are  there  in  a  common  plunger  force  pump  ? 
A.  Two  — a  receiving  and  a  discharge  valve. . 

Q.  How  are  they  located?  A.  One  on  the  suction  side,  the 
other  on  the  discharge. 

Q.  How  do  you  find  the  proper  size  of  safety  valves  for  boil- 
ers? A.  Three  square  feet  of  grate  surface  is  allowed  for  one 
inch  area  of  spring-loaded  valves,  or  two  square  feet  of  grate 
surface  to  one  inch  area  of  common  lever  valves. 

Q.  Give  the  reasons  why  pumps  do  not  work  sometimes?  A. 
Leak  in  suction,  leak  around  plunger,  leaky  check  valve,  or  valves 
out  of  order,  or  lift  too  long. 

Q.  How  often  ought  boilers  to  be  thoroughly  examined  and 
tested  ?  A.  Twice  a  year. 

Q.  How  would  you  test  them?  A.  With  hammer  and  with 
hydrostatic  test  —  using  warm  water. 


648  HANDBOOK    ON    ENGINEERING. 

Q.  Describe  the  single  acting  plunger  pump  ;  how  it  gets  and 
discharges  its  water?  A.  The  plunger  displaces  the  air  in  the 
suction  pipe,  causing  a  vacuum,  which  is  filled  by  the  atmosphere 
forcing  the  water  therein ;  the  receiving  valve  closes  and  the 
plunger  forces  the  water  out  through  the  discharge  valve. 

Q.  What  is  the  most  economical  boiler  feeder?  A.  An 
Exhaust  Injector. 

Q.  What  economy  is  there  in  the  Exhaust  Injector?  A. 
From  15  to  25  per  cent  saving  in  fuel. 

Q.  Where  is  the  best  place  to  enter  the  boiler  with  the  feed 
water?  A.  Below  the  water  level,  but  so  that  the  cold  water  can- 
not strike  hot  plates.  If  injector  is  used  this  is  not  so  material, 
as  the  feed  water  is  always  hot. 

Q.  What  are  the  principal  causes  of  priming  in  boilers?  A. 
Too  high  water,  not  steam  room  enough,  misconstruction,  engine 
too  large  for  boiler. 

Q.  How  do  you  change  the  water  in  the  boiler  when  steam  is 
up?  A.  By  putting  on  more  feed  and  opening  the  surface 
skimmer  or  blow-off  valve. 

Q.  If  the  safety  valve  was  stuck  how  would  you  relieve  the 
pressure  on  the  boiler  if  the  steam  was  up  and  could  not  make  its 
escape?  A.  Work  the  steam  off  with  engine  after  covering  fires 
heavy  with  coal  or  ashes,  and  when  the  boiler  is  sufficiently  cool, 
put  safety  valve  in  working  order. 

Q.  If  water  in  boiler  is  suffered  to  get  low,  what  may  be  the 
result?  A.  Burn  top  of  tubes,  perhaps  cause  an  explosion. 

Q.  If  water  is  allowed  to  get  too  high,  what  result?  A. 
Cause  priming,  perhaps  cause  breaking  of  cylinder  head. 

Q.  What  are  the  principal  causes  of  foaming  in  boilers?  A. 
Dirty  and  impure  water  and  animal  oil  or  grease. 

Q.  How  can  foaming  in  boilers  be  stopped?  A.  Close  throttle 
and  keep  closed  long  enough  to  show  true  level  of  water.  If  that 
level  is  sufficiently  high,  feeding  and  blowing  off  will  usually 
suffice  to  correct  the  evil. 


HANDBOOK   ON    ENGINEERING.  649 

Q,  What  would  you  do  if  you  should  find  your  water  gone 
from  sight  very  suddenly?  A.  If  a  light  fire  draw  and  cool  off 
as  quickly  as  possible  ;  if  a  heavy  fire  cover  with  wet  ashes  or 
slack  coal.  Never  open  or  close  any  outlets  of  steam  when  your 
water  is  out  of  sight. 

Q.  What  precautions  should  you  take  to  blow  down  a  part  of 
the  water  in  your  boiler  while  running  with  a  good  fire?  A. 
Never  leave  the  blow-off  valve,  and  watch  the  water  level. 

Q,  How  much  water  would  you  blow  off  at  once  while  running? 
A.  Never  blow  off  more  than  one  gauge  of  water  at  a  time  while 
running. 

Q.  What  precautions  should  the  engineer  take  when  necessary 
to  stop  with  heavy  fires?  A.  Close  dampers,  put  on  injector 
or  pump,  and  if  a  bleeder  is  attached,  use  it. 

Q.  What  is  an  engineer's  first  duty  on  entering  a  boiler-room? 
A.  To  ascertain  the  true  water  level,  and  look  at  steam  gauge. 

Q.  When  should  a  boiler  be  blown  out?  A.  After  it  is  cooled 
off  —  never  while  it  is  hot. 

Q.  When  laying  up  a  boiler  what  should  be  done?  A.  Clean 
thoroughly  inside  and  out;  remove  all  "Rust"  and  paint  rust 
places  with  red  lead ;  examine  all  stays  and  braces  to  see  if  any 
are  loose  or  badly  worn. 

Q.  Of  what  use  is  the  indicator?  A.  The  indicator  is  used  to 
determine  the  power  developed  by  an  engine,  to  serve  as  a  guide 
in  setting  valves  and  showing  the  action  of  steam  in  the  cylinder. 

Q.  How  would  you  increase  the  power  of  an  engine?  A.  To 
increase  the  power  of  an  engine,  increase  the  speed,  or  get  higher 
pressure  of  steam  ;  or  use  less  expansion. 

Q.  How  do  you  find  the  horse-power  of  an  engine? 
_  area  of  piston  X  M.E.P.  X  piston  speed. 

H*  P'  =  33,000. 

Q.  Which  has 'the  most  friction,  a  perfectly  fitted,  or  an  im- 
perfectly fitted  valve  or  bearing?  A.  An  imperfect  one. 


650  HANDBOOK    ON    ENGINEERING. 

Q.  How  hot  can  you  get  water  under  atmospheric  pressure  with 
exhaust  steam?  A.  212°. 

Q.  Does  pressure  have  any  influence  on  the  boiling  point?  A. 
Yes. 

Q.  Which  do  you  think  is  the  best  economy,  to  run  with  your 
throttle  wide  open  or  partly  shut?  A.  Always  have  the  throttle 
wide  open  on  a  governor  engine. 

Q.  At  what  temperature  has  iron  the  greatest  tensile  strength? 
A.  About  600°, 

Q.  About  how  many  pounds  of  water  are  required  to  yield  one 
horse-power  with  our  best  engines?  A.  From  15  to  30. 

Q.  What  is  meant  by  atmospheric  pressure?  A.  The  weight 
of  the  atmosphere. 

Q.  What  is  the  weight  of  atmosphere  at  sea  level?  A.  14.7 
pounds. 

Q.  What  is  the  coal  consumption  per  hour  per  indicated  horse- 
power? A.  Varies  from  1J  to  7  Ibs. 

Q.  What  is  the  consumption  of  coal  per  hour  on  a  square  foot 
of  grate  surface?  A.  From  10  to  12  Ibs. 

Q.  What  is  the  water  consumption  in  pounds  per  hour  per 
indicated  horse-power?  A.  From  15  to  45  Ibs. 

Q.  How  many  pounds  of  water  can  be  evaporated  with  one 
pound  of  best  soft  coal?  A.  From  7  to  10  Ibs. 

Q.  How  much  steam  will  one  cubic  inch  of  water  evaporate 
under  atmospheric  pressure?  A.  One  cubic  foot  of  steam 
(  approximately) . 

Q.  What  is  the  weight  of  a  cubic  foot  of  fresh  water?  A. 
62.425  Ibs. 

Q.  What  is  the  weight  of  a  cubic  foot  of  wrought  iron?  A. 
480  Ibs. 

Q.  What  is  the  last  thing  to  do  at  night  before  leaving  the 
plant?  A.  Look  around  for  greasy  waste,  hot  coals,  matches,  or 
anything  which  could  fire  the  building. 


HANDBOOK    ON    ENGINEERING.  651 

Q.  What  is  the  weight  of  a  square  foot  of  one-half  inch  boiler 
plate?  A.  20  Ibs. 

Q.  How  much  wood  equals  one  ton  of  soft  coal  for  steam  pur- 
poses? A.  About  4,000  Ibs.  of  wood. 

Q.  What  is  the  source  of  all  power  in  the  steam  engine?  A. 
The  heat  stored  up  in  the  coal. 

Q.  How  is  the  heat  liberated  from  the  coal  ?  A.  By  burning 
it  —  that  is,  by  combustion. 

Q.  Of  what  does  coal  consist?  A.  Carbon,  hydrogen,  nitro- 
gen, sulphur,  oxygen  and  ash. 

Q.  What  are  the  relative  proportions  of  these  that  enter  into 
coal?  A.  There  are  different  proportions  in  different  specimens 
of  coal,  but  the  following  shows  the  average  per  cent :  Carbon, 
80  ;  hydrogen,  5  ;  nitrogen,  1 ;  sulphur,  2  ;  oxygen,  7  ;  ash,  5. 

Q.  What  must  be  mixed  with  coal  before  it  will  burn?  A. 
Air. 

Q.  Of  what  is  air  composed?  A.  It  is  composed  of  nitrogen 
and  oxygen  in  the  proportion  of  77  per  cent  nitrogen  to  23  of 
oxygen. 

Q.  What  parts  of  the  air  mix  with  what  parts  of  coal?  A. 
The  oxygen  of  the  air  mixes  with  the  carbon  and  hydrogen  of  the 
coal. 

Q.  How  much  air  must  mix  with  coal  ?  A.  300  cubic  feet  of 
air  for  every  pound  of  coal. 

Q.  How  many  pounds  of  air  are  required  to  burn  one  pound  of 
carbon?  A.  From  20  to  24,  generally  taken  at  24. 

Q.  How  many  pounds  of  air  to  burn  one  pound  of  hydrogen? 
A.  Thirty-six. 

Q.  Is  hydrogen  hotter  than  carbon ?     A.  Yes,  41  times  hotter. 

Q.  What  part  of  the  coal  gives  out  the  most  heat?  A.  The 
hydrogen  does  part  for  part,  but  as  there  is  so  much  more  of 
carbon  than  hydrogen  in  the  coal,  we  get  the  greatest  amount  of 
heat  from  the  carbon. 


652  HANDBOOK    ON    ENGINEERING. 

Q.  In  how  many  different  ways  is  heat  transmitted?  A, 
Three,  by  radiation,  by  conduction  and  convection. 

Q.  If  the  fire  consisted  of  glowing  fuel,  show  how  the  heat 
enters  the  water  and  forms  steam?  A.  The  heat  from  the  glow- 
ing fuel  passes  by  radiation  through  the  air  space  above  the  fuel 
to  the  furnace  crown ;  there  it  passes  through  the  iron  of  the 
crown  by  conduction ;  there,  it  warms  the  water  resting  on  the 
crown,  which  then  rises  and  parts  with  its  heat  to  the  colder  water 
by  conduction  till  the  whole  mass  of  water  is  heated ;  then  the 
heated  water  rises  to  the  surface  and  parts  with  its  steam ,  so  a 
constant  circulation  is  maintained  by  convection, 

Q.  Of  what  does  water  consist?     A.  Oxygen  and  hydrogen. 

Q.  In  what  proportion?  A.  Eight  of  oxygen  to  one  of 
hydrogen,  by  weight. 

Q.  What  are  the  different  kinds  of  heat?  A.  Latent  heat, 
sensible  heat  and  sometimes,  total  heat. 

Q.  What  is  meant  by  latent  heat?  A.  Heat  that  does  not 
affect  the  thermometer  and  which  expends  itself  in  changing  the 
nature  of  a  body,  such  as  turning  ice  into  water  or  water  into  steam. 

Q.  Under  what  circumstances  do  bodies  get  latent  heat?  A. 
When  they  are  passing  from  a  solid  state  to  a  liquid  state,  or  from 
a  liquid  to  a  gaseous  state. 

Q.  How  can  latent  heat  be  recovered?  A.  By  bringing  the 
body  back  from  a  state  of  gas  to  a  liquid,  or  from  that  of  a  liquid 
to  that  of  a  solid. 

Q.  What  is  meant  by  a  thermal  unit?  A.  The  heat  necessary 
to  raise  one  pound  of  water,  at  any  temperature  —  one  degree 
Fan. 

Q.  If  the  power  is  in  coal,  why  should  we  use  steam?  A.  Be- 
cause, steam  has  some  properties  which  make  it  an  invaluable 
agent  for  applying  the  energy  of  the  heat  to  the  engine. 

Q.  What  is  steam?  A.  It  is  an  invisible  elastic  gas  generated 
from  water  by  the  application  of  heat. 

Q.  What  are  the  properties  which  make   it   so   valuable  to  us  ? 


HANDBOOK    ON    ENGINEERING.  653 

A..  1.  The  ease  with  which  we  can  condense  it.  2.  Its  great 
expansive  power.  3.  The  small  space  it  occupies  when  con- 
densed. 

Q.  Why  do  you  condense  the  steam?  A.  To  form  a  vacuum 
and  so  destroy  the  back  pressure  that  would  otherwise  be  on  the 
piston,  and  thus  get  more  useful  work  out  of  the  steam. 

Q.   What  is  vacuum?     A.  A  space  void  of  all  matter. 

Q.  How  do  you  maintain  a  vacuum?  A.  By  the  steam  used 
being  constantly  condensed  by  the  cold  water  or  cold  tubes,  and 
the  air  pump  constantly  clearing  the  condenser  out. 

Q.  Why  does  condensing  the  used  steam  form  a  vacuum?  A. 
Because  a  cubic  foot  of  steam  at  atmospheric  pressure  shrinks 
into  about  a  cubic  inch  of  water. 

Q.  What  do  you  understand  by  the  term  horse-power?  A.  A 
horse-power  is  equivalent  to  raising  33,000  Ibs.  one  foot  per  min- 
ute, or  550  Ibs.  raised  one  foot  per  second. 

Q.  What  do  you  understand  by  lead  on  an  engine's  valve?  A. 
Lead  on  a  valve  is  the  admission  of  steam  into  the  cylinder  be- 
fore the  piston  starts  its  stroke. 

Q.  What  is  the  clearance  of  a  cylinder  as  the  term  is  applied 
at  the  present  time:  A.  Clearance  is  the  space  between  the 
cylinder  head  and  the  piston  head,  with  ports  included. 

Q.  What  are  considered  the  greatest  improvements  on  the 
stationary  engine  in  the  last  forty  years?  A,  The  governor,  the 
Corliss  valve  gear,  and  the  triple  compound  expansion. 

Q.  What  is  meant  by  triple  expansion  engine?  A.  A  triple 
expansion  engine  has  three  cylinders,  using  the  steam  expansively 
in  each  one. 

Q.  Is  there  any  danger  of  a  well-fitted  and  tightly-keyed  fly- 
wheel coming  loose?  A.  Yes  ;  water  in  the  cylinder  by  produc- 
ing a  heavy  jar  would  tend  to  loosen  a  fly-wheel  and  frequently 
reversing  an  engine  under  a  load  and  high  speed,  would  tend  to 
produce  the  same  effect. 


654  HANDBOOK    ON    ENGINEERING. 

Q.  What  is  a  condenser  as  applied  to  an  engine?  A.  The  con- 
denser is  a  part  of  the  low-pressure  engine,  and  is  a  receptacle 
into  which  the  exhaust  enters  and  is  there  condensed. 

Q.  What  are  the  principles  which  distinguish  a  high-pressure 
from  a  low-pressure  engine?  A.  Where  no  condenser  is  used  and 
the  exhaust  steam  is  open  to  the  atmosphere. 

Q.  About  how  much  gain  is  there  by  using  the  condenser?  A. 
17  to  25  per  cent,  where  cost  of  water  is  not  figured. 

Q.  What  do  you  understand  by  the  use  of  steam  expansively? 
A.  Where  steam  admitted  at  a  certain  pressure  is  cut  off  and 
allowed  to  expand  to  a  lower  pressure. 

Q.  How  many  inches  of  vacuum  give  the  best  results  in  a  con- 
densing engine?  A.  Usually  considered  25". 

Q.  What  is  meant  by  a  horizontal  tandem  engine?  A.  One 
cylinder  being  behind  the  other,  with  two  pistons  on  same  rod. 

Q.  What  is  a  Corliss  valve  gear  ?  A.  (Describe  the  half  moon, 
or  crab-claw  gear,  or  oval-arm  gear  with  dash  pots.) 

Q.  From  what  cause  do  belts  have  the  power  to  drive  shafting? 
A.  By  friction  or  cohesion. 

Q.  What  do  you  understand  by  lap?  A.  Outside  lap  is  that 
portion  of  valve  which  extends  beyond  the  ports  when  valve  is 
placed  on  the  center  of  travel ;  and  inside  lap  is  that  portion  of 
valves  which  projects  over  the  ports  on  the  inside  or  towards  the 
middle  of  valve. 

Q.  What  is  the  use  of  inside  lap?  A.  To  give  the  engine 
compression. 

Q.  Where  is  the  dead  center  of  an  engine?  A.  The  point 
where  the  crank  and  the  piston  rod  are  in  the  same  right  line. 

Q.  In  what  position  would  you  place  an  engine  to  take  up  any 
lost  motion  of  the  reciprocating  parts  ?  A.  Place  the  engine  in 
the  position  where  the  least  wear  takes  place  on  the  journals. 
That  is,  in  taking  up  the  wear  of  crank-pin  brasses,  place  the 
engine  on  either  dead  center,  as  when  running,  there  is  little  wear 


HANDBOOK    ON    ENGINEERING.  655 

upon  the  crank-pin  at  these  points.  If  taking  up  the  cross-head 
pin  brasses  —  without  disconnecting  and  swinging  the  rod  — 
place  the  engine  at  half  stroke,  which  is  the  extreme  point  of 
swing  of  the  rod,  there  being  the  least  wear  on  the  brasses  and 
cross-head  pin  in  this  position. 

Q.  What  benefits  are  derived  from  using  fly-wheels  on  steam 
engines  ?  A.  The  energy  developed  in  the  cylinder  while  the  steam 
is  doing  its  work,  is  stored  up  in  the  fly-wheel,  and  given  out  by 
it  while  there  is  no  work  being  done  in  the  cylinder  —  that  is, 
when  the  engine  is  passing  the  dead  centers.  This  tends  to  keep 
the  speed  of  the  engine  shaft  steady. 

Q.  Name  several  kinds  of  reducing  motions,  as  used  in  indi- 
cator practice?  A.  The  pantograph,  the  pendulum,  the  brumbo 
pulley,  the  reducing  wheel. 

Q.  How  can  an  engineer  tell  from  an  indicator  diagram  whether 
the  piston  or  valves  are  leaking?  A.  Leaky  steam  valves  will 
cause  the  expansion  curve  to  become  convex ;  that  is,  it  will  not 
follow  hyperbolic  expansion,  and  will  also  show  increased  back 
pressure.  But  if  the  exhaust  valves  leak  also,  one  may  offset  the 
other,  and  the  indicator  diagram  would  show  no  leak.  A  leaky 
piston  can  be  detected  by  a  rapid  falling  in  the  pressure  on  the 
expansion  curve  immediately  after  the  point  of  cut-off.  It  will 
also  show  increased  back  pressure.  A  falling  in  pressure  in  the 
upper  portion  of  the  compression  curve  shows  a  leak  in  the  exhaust 
valve. 

Q.  What  would  be  the  best  method  of  treating  a  badly  scaled 
boiler,  that  was  to  be  cleaned  by  a  liberal  use  of  compound?  A. 
First,  open  the  boiler  up  and  note  where  the  loose  scale,  if  any, 
has  lodged.  Wash  out  thoroughly  and  put  in  the  required 
amount  of  compound.  While  the  boiler  is  in  service,  open  the 
blow-off  valve  for  a  few  seconds,  two  or  three  times  a  day,  to  be 
assured  that  it  does  not  become  stopped  up  with  scale.  After 
running  the  boiler  for  a  week,  shut  it  down,  and  when  the 


656  HANDBOOK    OX    ENGINEERING. 

pressure  is  down  and  the  boiler  cooled  off,  run  the  water  out  and 
take  off  the  hand-hole  plates.  Note  what  effect  the  compound 
has  had  on  the  scale,  and  where  the  disengaged  scale  has  lodged. 
Wash  out  thoroughly  and  use  judgment  as  to  whether  it  is  advis- 
able to  use  a  less  or  greater  quantity  of  compound,  or  to  add 
a  small  quantity  daily.  Continue  the  washing  out  at  short 
intervals,  as  many  boilers  have  been  buined  by  large  quan- 
tities of  scale  dropping  on  the  fire  sheets  and  not  being 
removed. 

Q.  What  is  an  engineer's  first  duty  upon  taking  charge  of  a 
steam  plant?  A.  The  first  duty  of  an  engineer  assuming  charge 
of  a  steam  plant  is  to  familiarize  himself  with  his  surroundings, 
ascertain  the  duty  required  of  each  and  every  piece  of  machinery 
contained  therein,  and  in  just  what  condition  each  one  is. 
Let  us  discuss  it  at  length,  assuming  that  when  just  engaged  he 
is  informed  as  to  the  nature  of  the  work  required  of  the  plant 
in  question,  namely:  Whether  it  is  a  heating  plant,  electric 
lighting,  hydraulic  or  electric  elevator,  power  station,  or  any 
other  kind  of  the  various  steam  plants  in  existence.  Of  course, 
a  great  deal  depends  upon  the  size  and  kind  of  plant  under  con- 
sideration and  the  number  of  men  employed,  hours  in  operation, 
and  some  other  things  in  general  which  most  engineers  know  of. 
He  should  first  see  just  what  his  plant  contains  "  from  cellar 
to  garret,"  so  to  speak ;  whether  all  that  is  contained  has  to  run 
continually,  or  almost  so,  and  what  can  be  depended  on  in  case 
anything  should  suddenly  become  deranged  or  give  out  entirely. 
Next,  he  should  ascertain  the  general  condition  of  everything, 
going  over  each  portion  in  turn,  as  time  and  opportunity  permit, 
and  conclude  from  what  he  has  seen  how  much  longer  it  may 
be  run  safely  and  economically.  It  will  be  remembered  that  a 
piece  of  machinery  may  be  run  safely  and  yet  not  with  economy. 
So,  if  he  should  wait  for  the  safety  limit  to  be  reached, 
without  taking  other  things  into  consideration,  he  might  wait 


HANDBOOK    OX    ENGINEERING.  657 

a  long  time  and  in  so  doing  waste  many  dollars  of  his 
employer's  money  before  it  was  thought  necessary  to  reno- 
vate, repair  or  renew.  In  going  over  everything,  examining 
?ach  part  critically,  it  would  be  well  to  make  copious  notes,  and, 
1  might  add,  sketches,  to  which  the  engineer  can  again  refer. 
It  sometimes  happens  that  engineers,  in  making  an  examination 
of  machinery,  do  not  take  dimensions  or  make  sketches  of  certain 
parts  which  have  to  be  repaired,  or  perhaps  renewed,  thinking 
that  the  next  time  the  apparatus  is  looked  at  will  do  for  that. 
3ow,  it  sometimes  happens  that  the  "  nekt  time  "  is  the  time 
when  some  accident  occurs,  finding  you  unprepared,  causing  con- 
fusion, in  the  midst  of  which  the  making  of  sketches  and  taking 
of  dimensions  cannot  be  thought  of.  All  such  should  be  done  at 
the  first  opportunity,  and  spare  parts  of  the  different  machinery 
should  be  kept  on  hand,  especially  in  the  case  of  a  plant  which 
has  only  the  machinery  which  is  constantly  in  use.  Another  point 
of  importance  to  which  an  engineer  should  give  attention,  is  to 
ascertain  the  quantity  and  kind  of  supplies  which  are  on  hand, 
that  he  may  know  when  to  make  requisition  for  more,  and  so  not 
run  short,  as  he  otherwise  might  do.  It  is  also  important  to  see 
what  tools  the  plant  contains  and  upon  what  you  can  depend  in 
case  of  the  break -down  of  any  part  of  the  machinery.  Of  course 
all  the  above  cannot  be  done  in  one  day,  but  no  time  should  be 
lost  in  doing  all  these  things  as  earh'  as  possible,  for  the  sooner 
you  get  all  the  particulars  and  details  of  your  plant  at  your 
"fingers'  ends,"  the  lighter  will  be  your  own  labors,  and  the 
more  free  will  your  mind  be  to  think  and  act  intelligently  for  the 
emergencies  of  the  future.  Therefore,  by  performing  this  first 
duty  as  early  and  thoroughly  as  possible,  the  succeeding  ones  will 
be  comparatively  easy  to  handle  and  perform,  for  the  reason  that 
you  will  be  prepared  for  them. 

Q.  Define  and  explain   the    difference    between    sensible  and 
latent  heat?     A.  The  difference  between  sensible  and  latent  heat 

42 


658  HANDBOOK    ON    ENGINEERING. 

is  explained  thus :  Sensible  heat  may  be  measured  with  a  ther- 
mometer, that  is,  it  affects  the  mercury  in  a  thermometer,  caus- 
ing it  to  rise  in  the  stem  so  that  the  degree  of  heat  may  be 
measured  on  the  graduated  scale  affixed.  Latent  heat  does  not 
affect  the  thermometer.  Bodies  get  latent  heat  when  they  are 
passing  from  a  solid  state  to  a  liquid  state,  and  also  when  passing 
from  a  liquid  to  a  gaseous  state ;  and  moreover,  this  latent  heat 
can  be  recovered  by  bringing  a  body  back  from  a  gaseous  to  a 
liquid  state,  and  from  liquid  to  solid.  Water  is  most  com- 
monly seen  under  the  'three  forms  of  matter  just  mentioned, 
namely,  solid,  ice  ;  liquid,  water  ;  gaseous,  steam.  The  following 
method  has  been  used  to  explain  how  latent  heat  exists: 
A  quantity  of  powdered  ice  is  placed  in  a  vessel  and  brought 
into  a  very  warm  room.  As  long  as  it  remains  as  ice,  it  may  be 
any  degree  of  heat  below  32°  Fahr.,  but  the  instant  it  begins  to 
melt,  owing  to  the  heat  of  the  room,  a  thermometer  placed  in  it 
will  record  32°  Fahr.  The  thermometer  will  continue  at  32°  as  long 
as  there  is  any  ice  in  the  vessel,  but  just  as  soon  as  the  last  piece  of 
ice  has  melted  it  will  begin  to  rise,  and  continue  to  do  so  until  the 
water  boils,  when  it  will  stand  at  212°  ;  but  although  the  water 
goes  on  receiving  heat  after  this,  the  instrument  will  stand  at  212° 
until  all  the  water  has  boiled  away.  Now,  a  great  amount  of  heat 
must  have  entered  the  water  since  the  ice  began  to  melt,  but  it  has 
no  effect  on  the  thermometer,  which  continues  at  32°,  as  noted 
above  ;  the  heat  that  has  so  entered  is  called  "  the  latent  heat  of 
water."  The  heat  that  has  entered  the  water  from  boiling 
till  it  all  becomes  steam  is  called  the  "latent  heat  of  steam." 
The  latent  heat  of  water  has  been  found  to  be  143°  Fahr. 
and  the  latent  heat  of  steam,  at  the  pressure  of  the  atmosphere, 
is  966°.  This  is  the  way  the  above  was  determined:  A 
quantity  of  water  at  a  temperature  of  32°  Fahr.  is  made  to 
boil,  and  the  time  taken  to  do  so  noted ;  in  this  case,  it  took  one 
hour.  The  water  must  be  kept  boiling  until  it  has  all  evaporated. 


HANDBOOK    ON    ENGINEERING.  659 

and  the  time  noted  from  boiling  till  evaporation,  which  in  this 
case  will  be  5^  hours.     Therefore, 

O  " 

Temperature  of  boiling  point, 212° 

Temperature  of  water  at  first. 32° 


Heat  that  has  entered  the  water  in  one  hour,     .  180° 

Number  of  hours  boiling, 0  5| 

900 
60 


Heat  that  has  entered  during  the  5-|  hours,  ,  960° 

From  this  we  see  that  the  heat  necessary  to  form  steam,  instead 
of  being  only  212°,  must  be  966°  -f  212°  =  1178°,  or  5J  times  as 
great.  Therefore,  if  it  were  not  for  latent  heat,  we  would  require 
to  burn  5|  times  the  amount  of  coal  that  we  now  do  to  generate 
steam.  The  sensible  and  latent  heats  alter  with  the  pressure,  but 
as  the  sensible  increases  the  latent  decreases,  and,  roughly 
speaking,  the  total  heat,  or  the  sum  of  the  two,  is  the  same.  In 
connection  with  the  foregoing  questions,  I  would  recommend  the 
reader  to  spend  a  little  time  in  looking  over  the  "  steam  tables," 
and  make  comparisons  between  the  different  quantities  noted 
therein.  By  so  doing  he  will  get  an  exact  knowledge  of  the  prop- 
erties of  saturated  steam. 

Q.  Explain  the  term  "  clearance,"  as  used  in  connection  with 
an  engine  cylinder  ?  A.  There  are  two  kinds  of  clearance,  cylinder 
clearance  and  piston  clearance .  Cylinder  clearance  means  the  space 
or  volume  which  exists  between  the  piston  and  the  valve,  when 
the  piston  is  exactly  at  the  beginning  of  the  stroke  and  the  crank 
is  on  the  dead  center.  This  volume  can  be  found  by  taking  care- 
ful and  exact  measurements  and  making  calculations  from  them, 
but  a  more  correct  way  is  to  fill  the  space  with  water,  noting  the 
quantity  used,  and  so  make  calculations  to  find  the  cubic  con- 


660  HANDBOOK    ON    ENGINEERING. 

tents.  The  cubic  contents  of  the  clearance  space  is  a  certain  per- 
centage of  the  total  volume  of  the  cylinder  itself  and  such  clear- 
ance is  expressed  as  so  much  per  cent.  This  clearance  causes  a 
small  loss  of  steam  each  stroke,  owing  to  the  difference  between 
the  initial  and  compressive  pressure.  Piston  clearance  is  the 
space  between  the  piston  and  cylinder  head  when  the  crank  is  on 
the  dead  center.  This  clearance  is  necessary  to  prevent  the 
cylinder  head  being  knocked  out,  in  case  of  an  unusual  quantity 
of  water  gaining  entrance  to  the  cylinder  while  the  engine  is 
running  at  its  usual  speed ;  and  also  to  admit  of  the  crank-pin 
and  wrist-pin  brasses  being  keyed  up  at  certain  intervals.  The 
way  to  find  the  piston  clearance  of  an  engine  is  as  follows: 
First,  disconnect  the  wrist-pin  end  of  the  connecting  rod  from 
the  cross-head,  and  with  a  bar  push  back  the  cross-head  until 
the  piston  strikes  the  cylinder  head ;  then  make  a  mark  with 
a  scriber  or  sharp  chisel,  on  both  the  sides  of  the  cross-head  and 
on  the  guide  in  which  the  cross-head  runs  ;  these  marks  must  be 
exactly  in  line  with  each  other  while  the  piston  is  in  the  above 
stated  position.  Next,  move  the  piston  to  the  other  end  of  the 
cylinder  till  it  strikes  the  head,  and  make  a  mark  on  the  guide 
similar  to  that  on  the  other  end,  using  the  same  mark  which  was 
made  on  the  cross-head.  The  new  mark  must  also  be  in  line  with 
this,  as  at  the  first  mentioned  end.  You  now  have  a  mark  at 
each  end  of  the  guide,  which  represents  the  place  at  which  the 
piston  strikes  the  cylinder  head,  when  they  alternately  coincide 
with  the  mark  on  the  cross-head  itself.  Now,  connect  the  rod 
to  the  cross-head  again  and  place  the  engine  or  crank  on  the  center. 
Next,  produce  or  extend  the  mark  on  the  cross-head  to  the  guide, 
this  time  using  a  pencil  instead  of  a  chisel  and  scriber.  The 
distance  between  the  new  pencil  mark  and  the  first  mark  made 
on  the  guide  is  the  amount  of  piston  clearance  which  exists  at 
that  end  of  the  cylinder.  Repeat  the  operation  on  the  other  end 
and  ycu  will  obtain  the  clearance  existing  there.  If  these  clear- 


HANDBOOK    ON    ENGINEERING.  661 

ances  are  not  equal,  as  indicated  by  the  marks,  make  them  so 
by  the  means  provided  for  in  the  design  of  the  piston  rod  and 
crosshead.  After  the  clearance  has  been  equalized,  the  pencil 
marks  may  be  obliterated  and  marks  similar  to  the  first  ones  may 
be  cut  in,  thus  leaving  a  permanent  mark  which  can  be  seen  while 
the  engine  is  running,  and  from  which  can  be  determined  whether 
the  clearance  is  lessening,  and  at  which  end. 

Q.  What  is  the  pressure  of  the  atmosphere  at  the  sea  level,  and 
how  determined?  A.  The  pressure  of  the  atmosphere  is  generally 
spoken  of  as  15  Ibs.  per  square  inch,  but  as  the  pressure  of  the 
atmosphere  is  constantly  varying  at  any  one  spot,  corrections 
have  to  be  made  according  to  the  reading  of  a  barometer. 
Generally  speaking,  15  is  as  nearly  correct  as  engineers  require 
it.  The  pressure  of  the  atmosphere  can  be  ascertained  by  the 
following  experiment:  Take  a  glass  tube  about  33  inches  long, 
having  a  bore  equal  to  a  square  inch  in  section.  Let  one  end  of 
the  tube  be  closed  in  or  capped,  so  that  it  can  contain  a  fluid. 
Then  fill  it  with  pure  mercury,  carefully  expelling  any  air  bub- 
bles. When  it  is  full,  cover  the  open  end  of  the  tube  with  a  piece 
of  glass  and  invert  the  whole  tube.  Place  the  open  end  into  a 
cup  of  mercury,  the  surface  of  which  is  subject  to  the  pressure  of 
the  air,  and  then  withdraw  the  piece  of  glass.  The  mercury  in 
the  tube  will  drop  about  three  inches  and  then  stop.  When  it 
has  ceased  to  fall,  again  cover  the  end  of  the  tube  with  the  glass. 
Lift  the  tube  out  of  the  cup  and  remove  the  glass  so  that  the 
mercury  may  run  out  into  a  scale-pan  provided  for  that  purpose. 
Upon  actually  weighing  the  mercury  lately  contained  in  the  tube, 
it  will  be  found  to  weigh  14.7  Ibs.  The  mercury  will  stop  falling 
in  the  tube  at  30  inches,  or  at  the  sea  level.  Hence,  we  know 
that  the  atmosphere  balances,  or  exerts  a  pressure  of  14. 7  Ibs. 
per  square  inch  at  the  sea  level. 

Q.  Upon  what  does  the  efficiency  of  a  surface  condenser  de- 
pend? A.  The  efficiency  of  a  surface  condenser  depends  upon: 


062  HANDBOOK    ON    ENGINEERING. 

1st,  the  proper  amount  of  cooling  surface ;  2d,  the  rapidity  with 
which  the  water  is  made  to  circulate  through  the  tubes  ;  3d,  the 
water  being  made  to  flow  in  an  opposite  direction  to  the  steam. 
The  temperature  of  the  circulating  water  also  has  a  bearing  on 
the  question,  as  it  is  obvious  that  the  colder  the  water  the  more 
effective  it  will  be  in  condensing  the  steam. 

Q.  A  feed  pump  has  a  steam  cylinder  of  6  inches  in  diameter, 
and  water  cylinder  of  4  inches  diameter ;  assuming  the  steam 
pressure  carried  to  be  80  Ibs.  per  square  inch  throughout  the 
stroke,  what  will  be  the  balancing  pressure  per  square  inch 
against  the  water  piston,  friction  being  entirely  neglected,  and 
gauge  pressure  being  used?  A.  In  this  question,  we  first  iind 
the  area,  the  number  of  square  inches  contained  in  the  steam 
piston.  Thus  :  The  diameter  —  6  in.  and  62  x  .7854  =  the  area. 
Worked  out  it  appears  thus :  62  means  that  6  is  to  be 
squared,  or  multiplied  by  itself,  or  6  x  6  =  36  square  inches, 
and  36  square  inches  multiplied  by  the  constant  .7854  = 
28.27  square  inches  area  contained  in  the  steam  piston. 
Since  the  pressure  is  stated  to  be  80  Ibs.  per  square  inch,  then 
28.2 7  x  80  =  total  pressure  on  the  piston  in  pounds,  or  2261.60 
Ibs.  Now,  we  will  find  the  area  of  the  water  piston,  which  is  4 
inches  in  diameter,  42  x  .7854  =  12.5664  square  inches  contained 
in  the  water  piston.  Therefore,  the  water  piston,  with  an  area 
of  12.56  sq.  in.,  has  to  have  a  resistance  against  which  it  will  act 
of  2261.60  Ibs.,  in  order  to  balance  the  pressure  against  the 
steam  piston.  Hence,  the  pressure  per  square  inch  can  be  found 
by  dividing  2261.60,  or  2261.60  divided  by  12.56  =  180  Ibs.  per 
square  inch,  the  balancing  pressure  on  the  4-inch  water  piston. 

Q.  State  what  you  consider  a  good  standard  of  strength  for 
steel  boiler  plate?  A.  The  American  Boiler  Makers'  standard, 
as  used,  is  as  follows :  Tensile  strength,  from  55,000  to  60,000 
Ibs.  per  square  inch  section ;  elongation  in  8  inches,  20  per  cent 
for  plates  |  inch  thick  and  under;  22  per  cent  for  plates  f  to  J 


HANDBOOK    ON    ENGINEERING.  663 

inches ;  25  per  cent  for  plates  £  inch  and  under ;  the  specimen 
test  piece  must  bend  back  on  itself  when  cold,  without  showing 
signs  of  fracture ;  for  plates  over  J  inch  thick,  specimens  must 
withstand  bending  180°  (or  half  way)  round  a  mandrel  11  times 
the  thickness  of  the  plate.  The  chemical  requirements  are  as 
follows:  Phosphorus,  not  over  .04  per  cent;  sulphur,  not  over 
.03  per  cent. 

Q.  What  is  meant  by  the  heating  surf  ace  of  a  boiler  ?  A.  The 
heating  surface  of  a  boiler  is  that  surface  of  plates  or  tubes  on 
one  side  of  which  is  water,  and  on  the  other  hot  gases.  It  has 
been  decided  that  the  surface  next  the  water  shall  be  reckoned, 
the  value  to  be  given  in  square  feet.  In  a  fire  tube,  or  tubular 
boiler,  it  will  include  the  under  side  of  the  shell  from  fire-line  to 
fire-line  (usually  about  one-half  of  it),  the  tubes  and  such  part  of 
the  back-tube  sheet  as  is  below  the  back  arch  and  not  taken  up 
by  the  tube  ends.  For  a  water-tube  boiler,  the  heating  sur- 
face will  include  the  tubes,  such  part  of  the  headers  as  are 
in  contact  with  the  hot  gases,  and  the  lower  part  (about  one- 
half)  of  the  steam  drum.  In  calculating  the  heating  surface, 
none  should  be  taken  which  has  steam  on  one  side  and  hot  gases 
on  the  other,  as  such  parts  tend  to  superheat  the  steam,  and  are 
known  as  superheating  surfaces. 

Q.  What  is  a  boiler  horse-power?  A.  A  boiler  horse-power 
has  been  recently  denned  as  the  evaporation  of  34£  pounds  of 
water  per  hour  from  a  feed  water  temperature  of  212°  Fahr. 
into  steam  at  a  temperature  of  2 12°  Fahr.,  and  at  a  pressure  of 
one  atmosphere.  Under  these  conditions  each  pound  of  water 
evaporated  will  take  up  966  heat  units,  and  the  34  J  Ibs.  will  take 
34J  x  966  =  33,327  heat  units  per  hour.  Hence,  to  find  the 
horse-power  of  a  boiler,  it  is  necessary  to  find  the  heat  units 
delivered  per  hour  to  the  water  and  divide  that  number  by  33,327. 

Q.  What  will  be  the  heating  surface  of  a  fire-tube  boiler  6 
feet  in  diameter,  having  150  tubes  3  inches  in  diameter  and  15 


664  HANDBOOK    ON    ENGINEERING. 

feet  long?  A.  Each  tube  will  have  a  heating  surface  equal  to  its 
outside  area,  since  the  water  is  on  the  outside  of  the  tubes.  The 
area  of  a  cylinder  3  in.  in  diameter  and  15  ft.  long  will  be  the 
circumference  times  the  length;  3  in.  —  1  ft.  and  the  circumfer- 
ence —  3.1416  xi  —  .7854  ft.;  this,  times  the  length  15  ft. 
=  11.78  sq.  ft.  for  one  tube :  for  150  tubes,  it  will  be  150  times 
that  =  1767  sq.  ft.  The  lower  half  of  the  shell  is  usually  con- 
sidered as  heating  surface.  The  circumference  of  a  circle  6  ft.  in 
diameter  is  6x3.1416  =18.85  ft.  and  the  area  of  the  shell  — 
18.85x15=282.75  sq.  ft.  Half  this  will  be  141.37  sq.  ft. 
For  the  back  end  or  tube  plate,  the  total  area  will  be  the  diameter 
squared  times  .7854  =  62  x  .7854  =  28.27  sq.  ft.  ;  f  of  this  will 
be  below  the  arch,  and  |  of  28.27  =-- 18.85  sq.  ft.  From  this 
must  be  subtracted  the -area  of  the  ends  of  the  tubes.  The  end 
area  of  one  tube  is  (J)2  x  .7854  =  .049  sq.  ft.,  and  for  150 
tubes  it  is  150  times  that,  or  7.35  sq.  ft.  The  heating  surface  of 
the  tube  plate  will  then  be  18.85  minus  7.35  —  11.5  sq.  ft.  The 
front  tube  plate  is  not  considered,  because  the  gases  are  cooled 
too  much  to  be  effective  by  the  time  they  have  passed  through 
the  tubes.  The  total  heating  surface  is  1767  +  141.37  -f  11.5 
=  1919.87  sq.  ft. 

Q.  On  what  does  the  efficiency  of  a  boiler  depend?  A.  The 
efficiency  of  any  piece  of  machinery  is  the  ratio  of  the  energy  made 
useful  to  that  furnished.  The  object  of  the  boiler  is  to  make  steam  ; 
hence,  the  enegy  used  is  that  which  has  gone  into  the  steam.  The 
proportion  of  the  heat  generated  in  the  furnace  which  is  transferred 
to-  the  steam,  will  depend  on  the  thickness  of  the  plates  of  the 
boiler,  on  their  condition  as  to  cleanliness,  on  the  amount  of  time 
during  which  the  gases  are  in  contact  with  the  plates  in  their 
passage  from  furnace  to  chimne}r,  on  the  completeness  with  which 
all  parts  of  the  gases  are  brought  in  contact  with  the  plates,  and  on 
the  temperature  of  the  hot  gases.  Evidently,  heat  will  pass  through 
a  thin  plate  more  readily  than  through  a  thick  one,  and  more 


HANDBOOK    ON     KM  JINK,  BRING.  665 

readily  through  a  clean  plate  than  through  one  on  which  a  non- 
conducting coating  of  soot  or  scale  has  formed  ;  the  more  time 
available  for  the  transfer  of  heat,  the  greater  will  be  the  amount 
transferred ;  the  more  complete  the  contact  between  plates  and 
gases,  the  more  opportunity  will  there  be  for  the  transfer  of  heat, 
and  the  higher  the  temperature  of  the  gases,  the  more  rapidly 
will  the  heat  be  transferred.  To  have  a  boiler  efficient,  it  is 
necessary  to  have  plenty  of  heating  surface,  so  that  the  hot  gases 
will  have  time  for  contact,  to  keep  the  plates  clean,  to  have  good 
circulation  of  the  gases,  and  to  keep  their  temperature  high  by 
preventing  radiation  and  allowing  as  little  air  to  enter  the  furnace 
as  is  needed  for  good  combustion.  The  efficiency  of  the  furnace, 
that  is,  the  ratio  of  the  heat  generated  in  the  furnace  to  that  con- 
tained in  the  coal,  is  a  separate  matter,  though  often  the  two  are 
lumped  together.  It  depends  on  the  adaptation  of  the  furnace  to 
the  kind  and  size  of  coal  used,  on  the  size  of  the  combustion 
chamber  and  on  the  proper  firing  of  the  coal. 

Q.  On  what  its  satisfactory  working?  A.  In  order  to 
work  satisfactorily,  a  boiler  must  not  only  be  efficient,  but  must 
make  steam  rapidly,  must  make  dry  steam,  must  be  easily  fired 
and  cleaned,  and  must  be  capable  of  standing  a  considerable 
amount  of  forcing  without  serious  priming.  To  get  rapid  steam 
making,  it  is  necessary  to  have  good  circulation  of  the  water  in  the 
boiler ;  to  get  dry  steam,  plenty  of  steam  space  is  needed,  so  that 
the  steam  may  circulate  slowly  and  allow  the  water  to  drop  out  of 
it ;  easy  firing  means  a  low  fire  door  of  good  size,  and  a  rather 
short  grate;  easy  cleaning  means  accessible  parts,  good  sized 
man-holes,  good  sized  and  well  placed  hand-holes,  a  large  blow- 
off  and  a  short  boiler ;  the  ,  prevention  of  priming  when  carrying 
an  overload  is  a  difficult  matter  ;  the  tendency  to  such  an  occur- 
rence depends  largely  on  the  feed-water  used ;  plenty  of  steam 
space  and  good  circulation  are  helpful,  but  some  waters  will  foam 
in  spite  of  all  precautions. 


666 


HANDBOOK    ON    ENGINEERING, 


Q.  Suppose  a  slide  valve  cutting  off  at  J  stroke,  and  a  |  cut- 
off is  desired,  how  would  you  proceed?  A.  Put  on  a  new  valve 
with  more  outside  lap.  This  would  require  a  greater  travel  of  the 
valve,  consequently,  I  would  increase  the  throw  of  the  eccentric, 
also. 

Q.  Which  requires  the  greater  outside  lap,  cutting  off  at  T9f.  of 
the  stroke,  or  cutting  off  at  J?  A.  Cutting  off  at  T9g.  The 
earlier  the  cut-off,  the  greater  should  be  the  outside  lap. 

Q.  Are  all  plain  slide  valves  made  alike,  as  regards  the  exhaust 
cavity  of  the  valve?  A.  No  ;  sometimes  they  are  made  "  line  and 
line  "  inside,  that  is,  the  width  of  the  exhaust  cavity  is  equal  to 
the  distance  between  the  inner  edges  of  the  two  steam  ports ;  and 
again,  the  width  of  the  exhaust  cavity  is  made  greater  or  less  than 
this  distance,  according  as  an  earlier  or  later  release  is  desired. 

Q.  What  is  the  effect  of  giving  inside  lap  to  a  slide  valve?  A. 
It  delays  the  release  and  increases  the  compression. 

Q.  What  is  the  effect  of  giving  inside  lead  to  a  slide  valve? 
A.  It  gives  an  early  release  and  decreases  the  compression. 

Q.  Suppose  a  simple  slide  valve  engine  with  a  fly-ball  governor, 
and  the  governor  belt  should  break  or  slip  off,  what  would 
happen  ?  A.  If  it  were  a  plain  governor  the  engine  would  race  ; 
but  if  a  governor  with  an  automatic  stop,  the  engine  would  slow 
down  and  stop. 

Q.  What  two  forces  are  opposed  to  each  other  in  a  case  of  fly- 
ball  governor?  A.  Centrifugal  force,  tending  to  throw  the  balls 
away  from  the  governor  staff,  and  the  force  of  gravity,  tending  to 
draw  the  balls  to  the  staff. 

Q.  What  other  name  is  given  to  a  fly-ball  governor?  A.  It  is 
also  called  a  throttling  governor,  because  the  steam  in  passing 
through  the  governor  valve  is  throttled,  choked,  or  wire- 
drawn. 

Q.  Are  all  fly-ball  governors  throttling  governors?  A.  No; 
the  governor  of  a  Porter- Allen  engine  and  those  of  all  Corliss 


HANDBOOK    ON    ENGINEERING.  667 

engines,  while  of  the  fly-ball   type,  are  not  throttling  governors, 
because  the  steam  does  not  pass  through  them. 

Q.  If  the  governor  shaft  of  a  fly-ball  governor  on  a  plain  slide- 
valve  engine  should  break,  could  the  engine  be  run?  A.  Yes; 
by  regulating  the  speed  of  the  engine  by  hand  at  the  throttle- 
valve. 

Q.  Describe  an  automatic  cut-off  engine?  A.  In  this  class  of 
engines,  as  the  load  on  the  .engine  becomes  greater  or  less,  the 
steam  entering  the  cylinder  is  cut  off  later  or  earlier,  and  it  is 
done  through  a  fly-ball  governor  in  the  case  of  a  Corliss  engine, 
or  through  a  shaft-governor  or  regulator  in  the  case  of  a  high- 
speed engine. 

Q.  In  an  automatic  cut-off  high-speed  engine  with  shaft-gov- 
ernor, is  the  eccentric  fastened  to  the  shaft?  A.  It  is  not.  It 
is  so  arranged  as  to  move  freely  across  the  shaft,  in  order  to  per- 
mit the  center  of  the  eccentric  to  approach  or  to  recede  from  the 
center  of  the  shaft,  according  as  the  load  on  the  engine  decreases 
or  is  increased.  And  herein  lies  the  chief  difference  between  a 
plain  slide-valve  and  an  automatic  cut-off  slide-valve  engine. 

Q.  If  the  connecting  rod  of  an  engine  had  box  liners  at  both 
ends  and  in  taking  it  down  the  liners  were  all  mixed  up,  how 
could  the  length  of  the  rod  from  center  to  center  of  boxes  be 
found?  A.  Put  the  cross-head  in  the  middle  of  its  stroke  - 
after  iindiug  the  piston  striking  points  —  and  then  measure  from 
the  center  of  the  cross-head  wrist  to  the  center  of  the  main  shaft. 
If  the  piston  clearance  at  both  ends  of  the  cylinder  is  known,  the 
piston  may  be  pushed  to  the  crank  end  of  the  cylinder  until  it 
touches  the  head,  and  the  distance  from  the  center  of  the  cross- 
head  wrist  to  the  center  of  the  main  shaft  found,  to  which  should 
be  added  the  length  or  throw  of  the  crank,  and  also  the  piston 
clearance  at  the  crank  end  of  the  cylinder. 

Q.  But  suppose  it  were  more  convenient  to  push  the  piston  to 
the  head  end  of  the  cylinder,  what  then?  A.  Find  the  distance 


668  HANDBOOK    ON    ENGINEERING. 

from  the  center  of  cross-head  wrist  to  center  of  main  shaft  and 
deduct  the  throw  of  the  crank,  and  also  the  clearance. 

Q.  How  is  the  length  of  the  valve  stem  and  of  the  eccentric 
rod  found  for  a  plain  slide  valve  engine  having  a  rock  shaft?  A. 
If  the  motion  of  the  slide  valve  is  parallel  with  the  motion  of  the 
piston,  the  length  of  the  valve  stem  may  be  found  by  measuring 
in  a  horizontal  line  from  the  center  of  the  valve  seat  to  the  center 
of  the  rock  shaft ;  and  for  the  eccentric  rod  by  measuring  from 
the  center  of  the  rock  shaft,  horizontally,  to  the  center  of  the 
main  shaft,  which  would  include  one-half  the  yoke. 

Q.  What  is  a  direct,  and  also  an  indirect  valve  motion;'  A. 
When  there  is  no  rock  shaft  between  the  eccentric  and  the  valve 
to  compound  the  motion,  it  is  called  "  direct,"  and  when  a  rock 
shaft  intervenes,  it  is  called  an  "  indirect  "  valve  motion. 

Q.  Is  the  valve  motion  of  a  Corliss  engine  direct  or  indirect? 
A.  It  is  direct. 

Q.  How  so ;  it  has  a  rock  shaft  between  the  eccentric  and 
the  wrist  plate?  A.  Even  so,  it  is  a  direct  valve  motion  ;  because 
all  connections  to  the  rock-shaft  arm  are  above  the  center  of  the 
shaft,  consequently,  the  motion  is  simple  and  not  compound. 

Q.  When  is  an  engine  said  to  "  run  under,"  and  when  to  "  run 
over?  "  A.  When  the  crank  pin  is  above  the  center  of  the  main 
shaft  and  the  pin  moves  towards  the  cylinder,  the  engine  is  said 
to  "  run  under ;  "  and  when  it  moves  away  from  the  cylinder,  the 
engine  is  said  to  "  run  over." 

Q.  What  is  meant  by  lead  of  valve,  and  what  is  it  for?  A. 
Lead  is  the  amount  that  the  port  is  open  to  steam  when  the  crank 
is  on  its  center.  It  is  given  in  order  to  allow  the  full  pressure  of 
steam  to  come  on  the  piston  at  the  beginning  of  the  stroke,  and 
to  provide  a  cushion  for  the  piston. 

Q.  Could  not  cushion  for  the  piston  be  obtained  in  some  other 
manner?  A.  Yes,  by  producing  compression  by  an  early  closing 
of  the  exhaust. 


HANDBOOK    ON    ENGINEERING. 

Q.  Suppose  a  slide  valve  had  f"  lap  and  no  lead,  and  it  was 
desired  to  give  it  -£s"  lead,  how  should  it  be  done?  A.  By  mov- 
ing- the  eccentric. 

Q.  Why  could  it  not  be  done  by  altering  the  length  of  the 
eccentric  rod  ?  A.  Because  the  eccentric  rod  does  not  establish 
the  amount  of  lead;  it  simply  equalizes  the  lead  given  by 
moving  eccentric. 

Q.  How  would  you  test  the  piston  of  :i  steam  engine  to  see 
whether  it  was  steam-tight  or  not?  A.  Put  the  crank  on  the 
outboard  center ;  remove  the  cylinder  head  on  the  head  end ; 
block  the  cross-head  and  admit  steam  to  the  crank-end  of 
cylinder  and  note  the  effect.  The  fly-wheel,  or  the  cross-head 
may  be  securely  blocked  and  the  piston  tested  in  this  manner  jit 
different  points  in  the  stroke, 

(^.  Why  aretwo  eccentrics  and  two  wrist  plates  put  on  some  Corliss 
engines?  A.  One  eccentric  is  for  the  induction  valves  to  lengthen 
the  range  of  the  cut-off  ;  the  other  for  the  exhaust  valves  to  admit 
of  early  release,  without  excessive  compression.  With  a  Corliss 
engine  having  but  one  eccentric,  the  limit  of  cut-off  is  at  less  than 
one-half  stroke,  but  with  two  eccentrics  the  cut-off  may  be  still 
later  in  the  stroke,  and  still  release  the  steam  at  the  proper  time. 

Q.  What  is  meant  by  a  *'  blocked  up  "  governor  en  a  Corliss 
engine?  A.  When  the  safety  stop  is  "  in  "  the  governor  is  said 
to  be  blocked  up. 

Q.  With  a  blocked  up  governor,  suppose  the  main  driving  belt 
should  break,  what  would  be  the  result?  A.  The  engine  would 
race  and  would,  perhaps,  be  wrecked. 

Q.  What  is  meant  by  the  fire  line  of  a  horizontal  cylindrical 
boiler?  A.  It  is  the  height  to  which  the  shell  is  exposed  to  the 
action  of  the  flames. 

Q.  How  high  should  the  fire  line  be  run?  A.  It  may  be  run  as 
high  as  the  lower  gauge  cock  water  level,  although  it  is  frequently 
run  no  higher  than  the  top  row  of  flues. 


670  HANDBOOK    ON    ENGINEERING. 

Q.  What  causes  a  chimney  or  smoke-stack  to  draw?  A.  The 
difference  in  the  temperature  of  the  air  inside  the  chimney  and 
that  outside.  The  air  inside  expands  and  exerts  less  pressure 
than  the  outside  air,  which  rushes  in  to  equalize  the  pressure. 

Q.  What  does  the  amount  of  grate  surface  determine?  A.  It 
determines  the  amount  of  coal  that  can  be  burned  per  hour,  and 
consequently,  the  amount  of  steam  that  can  be  generated. 

Q.  What  is  -the  object  in  giving  a  slide  valve  outside  lap?  A. 
To  save  steam  by  cutting  off  the  How  of  steam  into  the  cylinder 
before  the  piston  reaches  the  end  of  its  stroke.  For  example : 
WTith  24  in.  stroke  of  piston  and  |  cut-off,  the  flow  of  steam  to 
the  piston  is  cut  off  when  the  piston  has  moved  15  inches  and  it 
is  driven  the  remaining  9  inches  by  the  expansive  force  of  the 
steam. 

Q.  What  amount  of  refrigerating  water  is  required  for  a  con- 
denser? A.  For  a  surface  condenser  about  50  times,  and  for  a 
jet  condenser  30  times  the  amount  of  water  evaporated  in  the 
boiler ;  more  or  less  than  these  quantities  being  required  accord- 
ing to  the  temperature  of  the  exhaust  steam. 

Q.  Suppose  your  condenser  was  out  of  order  and  undergoing 
repairs,  could  you  run  the  engine?  A.  Yes;  by  attaching  an 
exhaust  pipe  to  the  engine  and  exhausting  into  the  atmosphere. 

Q.  With  a  lever  safety  valve,  should  the  end  of  the  valve  stem 
upon  which  the  lever  rests,  be  square  or  concave?  A.  Neither 
one ;  it  should  be  pointed,  so  that  the  lever  will  always  bear 
directly  on  a  line  with  the  center  of  the  valve  stem. 

Q.  Wrhat  is  the  proper  proportion  of  a  safety  valve  lever?  A,. 
About  7  to  1 ;  that  is,  if  the  distance  from  the  center  of  the 
valve  to  the  fulcrum  is  1  inch,  the  distance  from  the  center  of  the 
valve  to  the  end  of  the  long  arm  of  the  lever  should  be  about  7 
inches. 

Q.  How  should  the  grates  be  set  in  a  boiler  furnace?  A. 
They  should  be  set  level,  because  this  plan  will  enable  the  fire- 


HANDBOOK    ON    ENGINEERINGS 

man  to  more  easily  carry  a  bed  of  fuel  of  uniform  depth ;  besides, 
it  is  less  laborious  to  clean  the  fire  than  when  the  grates  are  lower 
at  the  bridge  wall. 

Q.  What  is  momentum?  A.  It  is  the  product  of  the  mass  or 
bulk  of  a  moving  body,  taken  in  pounds  or  tons,  multiplied  by  the 
velocity  of  the  moving  mass,  generally  taken  in  feet  per  second. 

Q.  Will  an  injector  work  at  the  same  steam  pressure  when  it 
lifts  the  water  as  when  the  water  flows  to  it  under  pressure?  A. 
No ;  when  the  water  flows  to  an  injector  under  pressure  it  will 
work  down  to  the  lowest  steam  pressures,  but  when  lifting  the 
water  it  requires  a  steam  pressure  of  ten  pounds  or  over  to  work 
the  injector. 

Q.  What  is  the  greatest  height  to  which  an  injector  will  lift 
water?  A.  That  depends  upon  the  starting  steam  pressure. 
There  are  injectors  that  will  lift  water  two  feet  with  10  Ibs. 
steam  pressure,  five  feet  with  30  Ibs.,  and  from  12  to  25  feet  with 
60  Ibs.  and  over. 

Q.  If  the  pulley  on  the  main  shaft  of  an  engine  driving  a  fly- 
ball  governor  be  reduced  in  diameter,  what  effect  will  it  have  on 
the  speed  of  the  engine?  A.  The  speed  of  the  engine  will  be 
increased. 

Q.  Which  is  the  greater,  the  bursting  or  the  collapsing  pressure 
of  a  boiler  tube?  A.  A  boiler  tube  will  collapse  under  less  pres- 
sure than  would  be  required  to  burst  it. 

Q.  Should  a  horizontal  externally  fired  boiler  be  set  level  or 
with  a  pitch?  A.  It  is  customary  to  set  such  a  boiler  one  inch 
lower  at  the  end  to  which  the  blow-off  pipe  is  attached,  in  order 
to  drain  the  boiler  readily. 

Q.  In  a  slide  valve  engine  with  a  connecting  rod,  will  the  valve 
cut  off  the  same  at  both  ends  of  the  stroke  if  it  has  equal  lap  and 
lead?  A.  No  ;  owing  to  the  angularity  of  the  connecting  rod. 

Q.  Is  it  proper  to  close  the  damper  with  a  banked  fire?  A. 
The  damper  should  never  be  closed  tightly  while  there  is  fire. 


672 


HANDBOOK    ON    ENGINEERING. 


CHAPTER     XXIII. 
INSTRUCTIONS  FOR  LINING   UP  EXTENSION  TO  LINE   SHAFT. 

The  erection  of  a  line  shaft,  or  an  extension  to  one,  is  a 
job  that  should  have  the  services  of  a  competent  millwright  or 
machinist,  as  it  is  one  calling  for  experience  and  considerable 
skill. 

I  will,  however,  give  you  some  pointers  on  how  to  proceed.  A 
linen  line  or  fine  wire  should  be  stretched  beneath  the  shaft  and 
parallel  to  it,  and  extending  beyond  the  termination  of  the 
extension. 


To  set  the  line  parallel  to  the  main  line  shaft,  hang  the  plumb- 
bobs  A  A  over  the  shaft,  as  shown  in  the  sketch,  and  then  adjust 
the  line  until  it  just  touches  the  lines  supporting  the  bobs,  with- 
out disturbing  their  position.  If  the  plumb-bobs  trouble  you  by 
swaying,  set  pails  of  water  so  that  the  bobs  will  be  immersed  ; 
this  will  stop  the  swaying  without  destroying  their  truth.  The 
plumb-bobs  may  just  as  well  be  old  nuts  or  similar  pieces  of  iron, 


HANDBOOK    ON    ENGINEERING.  673 

as  the  regulation  type,  since  the  result  will  be  exactly  the  same. 
After  getting  the  line  adjusted  to  the  desired  position,  suspend 
the  plumb-bobs  A  A  along  the  direction  of  the  extension,  so  that 
their  supporting  cords  will  just  touch  the  line  without  disturbing  it. 
The  new  section  of  the  shaft  is  now  brought  in  position  sideways 
until  it  also  touches  the  cords  of  the  plumb-bobs  A  A  ,  which,  of 
course,  locates  it  parallel  with  the  main  shaft  in  a  horizontal  plane. 
To  get  it  to  the  right  height,  enter  the  shaft  coupling  of  the  new 
part  into  coupling  of  the  main  shaft,  and  then  adjust  until  the 
shaft  shows  level  when  tested  with  an  accurate  spirit  level.  A 
level  suitable  for  this  work  should  be  of  iron  and  planed  on  the 
under  side  with  a  V-groove,  which  will  always  locate  it  parallel 
with  the  shaft  when  testing  it.  Before  leveling  the  new  part  of 
the  shaft,  it  will  be  necessary  to  try  the  shaft  already  in  position, 
as  it  may  not  be  level.  If  found  "out"  it  should  be  leveled, 
but  sometimes  this  will  not  be  possible  or  feasible,  in  which  case 
it  will  be  necessary  to  set  the  new  part  at  the  same  inclination. 
To  do  this,  test  the  main  shaft  and  find  how  much  it  is  out,  and 
adjust  the  level  by  strips  of  paper  until  it  shows  "fair."  The 
paper  should  be  secured  to  the  level  by  glue  or  other  means  and 
used  on  the  new  shaft  in  that  condition,  always  keeping  the  level 
with  the  "  packed"  end  pointing  in  the  same  direction.  After 
getting  the  new  part  in  position,  it  is  well  to  test  it  before  con- 
necting it  to  the  main  part  ;  that  is,  it  should  be  turned  by  hand 
to  determine  if  the  frictional  resistance  is  excessive  or  not.  After 
connecting  with  the  main  part,  it  is  not  a  bad  idea  to  test  it  again 
by  hand,  if  possible.  With  a  long  shaft  it  may  be  necessary  to 
disconnect  the  further  sections  and  remove  the  belts  from  the 
connected  machines.  In  this  way  a  fair  idea  of  the  frictional 
resistance  may  be  obtained.  As  before  stated,  this  work  requires 
experience  and  skill,  and  should  properly  be  done  by  one  thor- 
oughly competent  for  the  work  ;  for,  while  his  services  may  seem 
a  trifle  expensive,  it  will  usually  be  found  to  pay  better  in  the 

43 


674  HANDBOOK    ON    ENGINEERING. 

long  run,  as  the  frictional  resistance  of  an  improperly  lined  shaft 
will  quickly  consume  coal  enough  to  pay  the  difference. 

SIMPLICITY  IN  STEAM   PIPING. 

In  building  steam  power  plants,  and  especially  in  arranging 
the  piping  connections  for  them,  simplicity  is  a  characteristic  the 
value  of  which  is  often  too  little  appreciated.  It  should  be  borne 
in  mind  that  extra  valves  and  duplicate  piping  mean  a  very 
considerable  amount  of  capital  lying  at  waste  to  meet  a  contin- 
gency which  may,  in  all  probability,  never  arise,  not  to  speak  of 
the  care  and  attention  required  to  keep  piping  and  valves  which 
are  rarely  used  in  shape  for  service.  Another  point  which  ought 
to  be  realized  in  the  design  of  piping,  is  that  every  square  foot  of 
uncovered  surface,  as  in  flanges  and  the  like,  causes  the  loss  of 
about  one  dollar  per  year  in  condensation  of  steam ,  and  each  square 
foot  of  uncovered  surface  represents  the  loss  of  nearly  one-quarter 
of  this  amount.  The  principle  of  construction  is  to  design  the 
piping  with  the  utmost  simplicity  possible  ;  without  any  double 
connections,  put  it  up  so  that  no  accidents  can  happen  to  it.  It 
is  argued  that  this  is  impossible,  but  it  is  equally  impossible  to 
insure  absolute  immunity  against  "  shut  downs,"  of  greater  or 
less  duration,  by  any  amount  of  duplex  connections,  for  even 
the  blowing  out  of  a  single  gasket  can  blow  down  a  whole  battery 
of  boilers  before  a  12 -inch  valve  can  be  closed  and  another 
opened.  With  the  more  extensive  introduction  of  high-pressure 
valves  and  fittings,  it  is  possible,  by  proper  design,  to  reduce 
the  liability  to  accident  very  nearly  to  the  point  of  absolute 
safety,  and  by  the  introduction  of  one  or  two  extra  valves,  it  is 
generally  possible  to  divide  the  plant  into  sections,  any  one  of 
which  can,  if  occasion  demands,  be  operated  independently.  No 
fixed  rules  can  be  laid  down  and  the  line  between  absolute  sim- 
plicity and  necessary  complexity  must  be  drawn  separately  for 
each  plant  with  due  regard  to  the  work  it  has  to  perform ,  but  it 


HANDBOOK    ON    ENGINEERING. 


675 


should  be  remembered  that  the  rnor^  simple  a  plant  can  be  made 
to  accomplish  the  work  with  absolute  reliability,  the  greater  the 
achievement  in  economy  of  first  cost,  and  in  availability  arid 
economy  of  operation. 


Diagram  Showing  Screwed  Valve  and  Fittings 


Diagram  Showing  Flanged  Valve  and  Fittings 


CUTTING   PIPE  TO   ORDER. 

In  placing"  orders  for  pipe,  a  diagram  should  be  made,  accord- 
ing to  above  cuts.  Great  care  should  be  taken  in  making  a 
diagram  for  large  pipe  ;  all  measurements  should  be  from  centers. 
When  flanged  fittings  are  used,  state  if  desired  drilled,  and  if 
with  bolts  and  gaskets  complete.  Also  state  if  you  desire  the 


676 


HANDBOOK    ON    ENGINEERING. 


fittings  made  up  tight,  and  mark  such  pieces  at  point  joint  is 
desired,  on  diagram. 

FEED=WATER  REQUIRED   BY   SHALL  ENGINES. 


Pounds  of  Water 

Pounds   ol    Water 

Pressure  of  Steam 

per     Effective 

Pressure  of  Steam 

per    Effective 

in  Boiler,  by 

Horse  -power  per 

in  Boiler,  by 

Horse-  power  per 

Gauge. 

Hour. 

Gauge. 

Hour. 

10 

118 

60 

75 

.  15 

111 

70 

71 

20 

105 

80 

68 

25 

100 

90 

65 

30 

93 

100 

63 

40 

84 

120 

61 

50 

79 

160 

58 

HEATING   FEED-WATER. 

Feed-water,  as  it  comes  from  the  wells  or  hydrants,  has  ordi- 
narily a  temperature  of  from  35°  in  winter  to  from  60  to  70°  in 
summer.  Much  fuel  can  be  saved  by  heating  this  water  by  the 
exhaust  steam,  whose  heat  would  otherwise  be  wasted.  Until 
quite  recently,  only  non-condensing  engines  utilized  feed  water 
heaters  but  lately  they  have  been  introduced  with  success  between 
the  cylinder  and  the  air-pump  in  condensing  engines.  The 
saving  in  fuel  due  to  heating  feed-water  is  given  on  page  644. 


RATING   BOILERS   BY   FEED-WATER. 

The  rating1  of  boilers  has,  since  the  Centennial  Exposition  in 
1876,  been  generally  based  on  30  pounds  feed  water  per  hour  per 
horse-power.  This  is  a  fair  average  for  good  non-condensing  engines 
working  under  about  70  to  100  ponnds  pressure.  But  different 


HANDBOOK   ON     ENGINEERING. 


677 


pressures  and  different  rates  of  expansion  change  the  require- 
ments for  feed  water.  The  following  table  gives  Prof.  R.  H. 
Thurston's  estimate  of  the  steam  consumption  for  the  best  classes 
of  engines  in  common  use  when  of  moderate  size  and  in  good 
order :  — 

WEIGHTS  OF  FEED  WATER  AND  OF  STEAM. 

NON  CONDENSING   ENGINES.  —  R.    H.    T. 


Steam  Pressure. 

Lbs.  per  H.  P.  per  Hour.  —  Ratio  of  Expansion. 

Atmos- 
phere. 

Lbs.  per 
sq.  in. 

2 

3 

4 

C 

7 

10 

3 

45 

40 

39 

40 

40 

42 

45 

4 

60 

35 

34 

36 

36 

38 

40 

5 

75 

30 

28 

27 

26 

30 

32 

6 

90 

28 

27 

26 

25 

27 

29 

7 

105 

26 

25 

24 

23 

25 

27 

8 

120 

25 

24 

23 

22 

22 

21 

10 

150 

24 

23 

22 

21 

20 

20 

CONDENSING    ENGINES. 


2 

30 

30 

28 

28 

30 

35 

40 

3 

45 

28 

27 

27 

26 

28 

32 

4 

60 

27 

26 

25 

24 

25 

27 

5 

75 

26 

25 

25 

23 

22 

24 

6 

90 

26 

24 

24 

22 

21 

20 

8 

120 

25 

23 

23 

22 

21 

20 

10 

150 

25 

23 

22 

21 

20 

19 

Small  engines  having  greater  proportional  losses  in  friction,  in 
leaks,  in  radiation,  etc.,  and  besides  receiving  generally  less  care 


678  HANDBOOK    ON    ENGINEERING. 

in  construction  and  running  than  larger  ones,   require  more  feed 
water  (or  steam)  per  hour, 

FEED-WATER   HEATERS. 

Inattention  to  the  temperature  of  feed  water  for  boilers  is  en- 
tirely too  common,  as  the  saving  in  fuel  that  may  be  effected  by 
thoroughly  heating  the  feed  water  —  by  means  of  the  exhaust 
steam  in  a  properly  constructed  heater  —  would  be  immense,  as 
may  be  seen  from  the  following  facts :  A  pound  of  feed  water  en- 
tering a  steam  boiler  at  a  temperature  of  50°  Fahr.,  and  evapo- 
rating into  steam  of  60  Ibs.  pressure,  requires  as  much  heat  as 
would  raise  1157  Ibs.  of  water  1  degree.  A  pound  of  feed  water 
raised  from  50°  Fahr.  to  220°  Fahr.  requires  987  thermal  units 
of  heat,  which  if  absorbed  from  exhaust  steam  passing  through  a 
heater,  would  be  a  saving  of  15  per  cent  in  fuel.  Feed  water  at  a 
temperature  of  200°  Fahr.,  entering  a  boiler,  as  compared  in  point 
of  economy,  with  feed  water  at  50°,  would  effect  a  saving  of  over 
13  per  cent  in  fuel ;  and  with  a  well-constructed  heater  there  ought 
to  be  no  trouble  in  raising  the  feed  water  to  a  temperature  of  212° 
Fahr.  If  we  take  the  normal  temperature  of  the  feed  water  at  60°, 
the  temperature  of  the  heated  water  at  212°  and  the  boiler  pressure 
at  20  Ibs.,  the  total  heat  imparted  to  the  steam  in  one  case  is 
1192.5°  minus  60°  =  1132.5° ;  and  in  the  other  case,  1192.5° 
minus  212°  —  980.5°,  the  difference  being  152°,  or  a  saving  of 
152/1132.5  =  13.4  per  cent.  Supposing  the  feed  water  to  enter 
the  boiler  at  a  temperature  of  32°  Fahr.,  each  pound  of  water  will 
require  about  1200  units  of  heat  to  convert  it  into  steam,  so  that 
the  boiler  will  evaporate  between  6|  and  7J  Ibs.  of  water  per 
pound  of  coal.  The  amount  of  heat  required  to  convert  a  pound 
of  water  into  steam  varies  with  the  pressure,  as  will  be  seen  by 
the  following  table :  — 


HANDBOOK    ON    ENGINEERING. 


679 


TABLE  SHOWING  THE  UNITS  OF  HEAT  REQUIRED  TO  CONVERT  ONE  POUND 
OF  WATER,  AT  THE  TEMPERATURE  OF  32°  FAHR.,  INTO  STEAM  AT 
DIFFERENT  PRESSURES. 


Pressure  of 

Pressure  of 

Steam  in  Ibs.  per 

Units  of  Heat. 

Steam  in  Ibs.  per 

Units  of  Heat. 

Sq.  In.  by  Gauge. 

Sq.  In.  by  Gauge. 

1 

,148 

110 

,187 

10 

,155 

120 

,189 

20 

,161 

130 

,190 

30 

,165 

140 

,192 

40 

,169 

150 

,193 

50 

,173 

160 

,195 

60 

,176 

170 

,196 

70 

,178 

180 

,198 

80 

,181 

190 

1,199 

90 

,183 

200 

1,200 

100 

,185 

If  the  feed  water  has  any  other  temperature  the  heat  necessary 
to  convert  it  into  steam  can  easily  be  computed.  Suppose,  for 
instance,  that  its  temperature  is  65°,  and  that  it  is  to  be  converted 
into  steam  having  a  pressure  of  80  Ibs.  per  square  inch.  The 
difference  between  65  and  32  is  33  ;  and  subtracting  this  from 
1181  (the  number  of  units  of  heat  required  for  feed  water  hav- 
ing a  temperature  of  32°),  the  remainder,  1148,  is  the  number  of 
units  for  feed  water  with  the  given  temperature.  Yet  it  must  be 
understood  that  any  design  of  heater  that  offers  such  resistance 
to  the  free  escape  of  the  exhaust  steam  as  to  neutralize  the  gain 
that  would  otherwise  be  obtained  from  its  use,  ought  to  be 
avoided,  as  the  loss  occasioned  by  back  pressure  on  the  exhaust, 
in  many  instances,  counteracts  the  advantages  derived  from  the 
heating  of  the  feed  water. 


Feed-water  heaters   are  a   most  important  feature  of  a  good 
steam  plant.     First,  by  utilizing  the  heat   of  the   exhaust    steam 


680 


HANDBOOK    ON    ENGINEERING. 


from  the  engine  or  waste  gases  in  chimney,  the  feed  water  may  be 
heated  to  about  210°  Fahr.,  with  ease,  before  entering  boilers, 
by  this  means  saving  fuel  and  increasing  capacity  of  boiler. 
Second.  By  heating  the  water,  the  boilers  are  protected  from 
serious  and  unequal  strain,  as  the  difference  of  temperature  be- 
tween incoming  water  and  outgoing  steam  may  be  kept  about  110 
(210°  to  320°).  Third.  Every  heater  must  necessarily  be  a 
water  purifier,  as  the  mud  and  lime  are  eliminated,  to  some  degree 
at  least,  before  the  water  reaches  the  boiler, by  heat. 

TABLE. 

SHOWING  GAIN  IN  USE.  OF  FEED  WATER  HEATER.  PERCENTAGE  OF 
HEAT  REQUIRED  TO  HEAT  WATER  FOR  DIFFERENT  FEDD  AND  UOILILN 
TEMPERATURES,  AS  COMPARED  WITH  A  FEED  AND  BOILING  TEM- 
PERATURE OF  212°. 


Boiling 

Initial  Temperature  of  feed  water. 

"P/-*i  r»  t- 

irOlDL, 

Fahr. 

32° 

50° 

68° 

86° 

104° 

122° 

140° 

158° 

176° 

194° 

212° 

212 

1.19 

.17 

1.15 

1.13 

.11 

1.10 

1.08 

1.06 

.04 

1.02 

1.00 

230 

1.20 

.18 

1.16 

1.14 

.12 

1.10 

1.08 

1.06 

.04 

1.02 

1.01 

248 

1.20 

.18 

1.16 

1.14 

.13 

1.11 

1.09 

1.07 

.05 

1.03 

1.01 

266 

1.21 

.19 

1.17 

1.  15 

.13 

1.11 

1.09 

1.07 

.06 

1.04 

1.02 

284 

1.21 

.20 

1.18 

1.16 

.14 

1.12 

1.10 

1.08 

.06 

.04 

1.02 

302 

1.22 

.20 

1.18 

1.16 

.14 

1.12 

1.11 

1.09 

.07 

.05 

1.03 

320 

1.22 

.21 

1.19 

1.17 

.15 

1.13 

1.11 

1.09 

.07 

.05 

1.03 

338 

1.23 

.21 

1.19 

1.17 

.15 

1.14 

1.12 

1.10 

.08 

.06 

1.04 

356 

1.23 

.22 

1.20 

1.18 

.16 

1.14 

1.12 

1.10 

.08 

.06 

1.04 

374 

1.24 

.22 

1.20 

1.18 

.17 

1.15 

1.13 

1.11 

.09 

.07 

1.05 

392 

1.24 

.23 

1.21 

1.19 

.17 

1.15 

1.13 

1.11 

.09 

.07 

1.06 

410 

1.25 

.23 

1.22 

1.20 

.18 

1.16 

1.14 

1.12 

.10 

.08 

1.06 

428 

1.25 

.24 

1.22 

1.20 

.18 

1.16 

1.14 

1.12 

.11 

.09 

1.07 

There  are  two  distinct  types  of  heaters  in  which  heat  is  derived 
from  exhaust  steam.  These  are  known  as  closed  and  open 
heaters.  Each  has  its  advantages  and  disadvantages.  The 
closed  heater  is  constructed  so  that  the  water  is  forced  under  pres- 


HANDBOOK    ON    ENGINEERING.  681 

sure  through  tubes  or  chambers  surrounded  by  the  exhaust  steam, 
the  heat  being  transmitted  through  the  walls  of  the  tubes  and  cham- 
bers. The  open  heater  is  a  vessel  in  which  the  feed  water  comes 
into  direct  contact  with  the  exhaust  steam,  by  spraying  or  inter- 
mingling. The  heated  water  is  pumped  hot  into  the  boiler. 
The  closed  heater  has  the  advantage  of  permitting  the  water  to 
pass  through  the  pump  cold  and  in  that  state  is  easily  handled. 
To  pump  hot  water  from  an  open  heater  requires  special  care  in 
piping  and  packing  the  feed-pump.  The  closed  heater,  being  a 
purifier  (if  any  lime  is  present  in  water,  a  portion  is  bound  to  be 
precipitated  by  heat),  should  be  cleaned,  a  job  about  as  difficult 
as  cleaning  a  boiler ;  or  blown  out,  which  is  never  a  satisfactory 
method.  In  the  precipitation  of  lime  by  heat,  carbonic  acid  gas 
is  set  free  and  chemists  say  that  this  gas  in  a  nascent  state  (just 
being  born)  attacks  iron  and  brass.  Whatever  the  cause,  experi- 
ence has  demonstrated  that  ordinary  wrought  iron,  steel  and 
brass,  corrode  under  this  action.  The  open  heater,  being  usually 
a  large  chamber,  is  accessible  for  cleaning  out,  and  if  made  with 
ordinary  care  will  last  a  long  time.  A  leak  in  it  is  not  a  serious 
matter,  while  a  leak  in  the  closed  heater  means  a  waste  of  hot 
water  into  the  exhaust  pipe.  The  open  heater  has,  at  times, 
been  the  cause  of  serious  mishaps.  In  it  the  steam  and  water 
mix ;  with  any  stoppage  in  exit  of  feed-water,  there  is  danger 
of  flooding  the  cylinder  of  the  steam  engine  through  exhaust 
pipe,  causing  a  wreck.  The  more  modern  forms  of  these  heaters 
and  the  experience  obtained  in  their  use  have  reduced  this 
difficulty  to  a  minimum. 

WATER. 

Pure  water  at  62°  F.  weighs  62.355  pounds  per  cubic  foot,  or 
8|  Ibs.  per  U.  S.  gallon;  7.48  gallons  equal  1  cu.  ft.  It  takes 
30  Ibs.,  or  3.6  gal.  for  each  horse-power  per  hour.  It  would  be 
difficult  to  get  at  the  total  daily  horse-power  of  steam  used  in  the 


682  HANDBOOK    ON    ENGINEERING. 

U.  S.,  but  it  reaches  into  the  billions  of  gallons  of  feed  water  per 
day.  The  importance  of  knowing  what  impurities  exist  in  most 
feed  waters,  how  these  act  on  a  boiler  and  how  they  may  be  re- 
moved is,  therefore,  patent  to  every  intelligent  engineer.  I  give 
therefore,  the  thoughts  of  some  prominent  investigators  on  the 
subject. 

Prof.  Thurston  says  :  — 

"  Incrustation  and  sediment  are  deposited  in  boilers,  the  one 
by  the  precipitation  of  mineral  or  other  salts  previously  held  in 
solution  in  the  feed-water,  the  other  by  the- deposition  of  mineral 
insoluble  matters,  usually  earths,  carried  into  it  in  suspension  or 
mechanical  admixture.  Occasionably  also,  vegetable  matter  of  a 
glutinous  nature  is  held  in  solution  in  the  feed  water,  and,  pre- 
cipitated by  heat  or  concentration,  covers  the  heating  surfaces 
with  a  coating  almost  impermeable  to  heat,  and  hence,  liable  to 
cause  an  overheating  that  may  be  very  dangerous  to  the  struc- 
ture. A  powdery  mineral  deposit  sometimes  met  with  is  equally 
dangerous,  and  for  the  same  reason.  THE  ANIMAL  AND  VEGE- 
TABLE OILS  AND  GREASES  CARRIED  OVER  FROM  THE  CONDENSER  OR 
FEED  WATER  HEATER  ARE  ALSO  VERY  LIKELY  TO  CAUSE  TROUBLE. 

Only  mineral  oils  should  be  permitted  to  be  thus  introduced,  and 
that  in  minimum  quantity.  Both  the  efficiency  and  safety  of  the 
boiler  are  endangered  by  any  of  these  deposits. 

"  The  amount  of  the  foreign  matter  brought  into  the  steam 
boiler  is  often  enormously  great.  A  boiler  of  100  horse-power 
uses,  as  an  average,  probably  a  ton  and  a  half  of  water  per 
hour,  or  not  far  from  400  tons  per  month,  steaming  ten  hours 
per  day ;  and  even  with  the  water  as  pure  as  the  Croton  at 
New  York,  receives  90  pounds  of  mineral  matter,  and  from 
many  spring  waters  a  ton,  which  must  be  either  blown  out  or 
deposited.  These  impurities  are  usually  either  calcium  carbon- 
ate or  calcium  sulphate,  or  a  mixture ;  the  first  is  most  com- 
mon on  land,  the  second  at  sea.  Organic  matters  often 


HANDBOOK    ON    ENGINEERING. 

harden    these  mineral  scales  and  make    them    more    difficult  of 
removal. 

"  The  only  positive  and  certain  remedy  for  incrustation  and 
sediment,  once  deposited,  is  periodical  removal  by  mechanical 
means  at  sufficiently  frequent  intervals  to  insure  against  injury  by 
too  great  accumulation.  Between  times,  some  good  may  be  done 
by  special  expedients  suited  to  the  individual  case.  No  one 
process  and  no  one  antidote  will  suffice  for  all  cases. 

"  Where  carbonate  of  lime  exists,  sal-ammoniac  may  be  used 
as  a  preventive  of  incrustation,  a  double  decomposition  occur- 
ring resulting  in  the  production  of  ammonia  carbonate  and 
calcium  chloride  —  both  of  which  are  soluble,  and  the  first  of 
which  is  volatile.  The  bicarbonate  may  be  in  part  precipitated 
before  use  by  heating  to  the  boiling  point,  and  thus  breaking 
up  the  salt  and  precipitating  the  insoluble  carbonate.  Solutions 
of  caustic  lime  and  metallic  zinc  act  in  the  same  manner. 
Waters  containing  tannic  acid  and  the  acid  juices  of  oak, 
sumach,  logwood,  hemlock,  and  other  woods,  are  sometimes 
employed,  but  are  apt  to  injure  the  iron  of  the  boiler,  as  may 
acetic  or  other  acid  contained  in  the  various  saccharine  matters 
often  introduced  into  the  boiler  to  prevent  scale,  and  which 
also  make  the  lime-sulphate  scale  more  troublesome  than  when 
clean.  Organic  matter  should  never  be  used. 

' '  The  sulphate  scale  is  sometimes  attacked  by  the  carbonate  of 
soda,  the  products  being  a  soluble  sodium  sulphate  and  a  pulver-. 
ulent  insoluble  calcium  carbonate,  which  settles  to  the  bottom  like 
other  sediments  and  is  easily  washed  off  the  heating  surfaces. 
Barium  chloride  acts  similarly,  producing  barium  sulphate  and 
calcium  chloride.  All  the  alkalies  are  used  at  times  to  reduce 
incrustations  of  calcium  sulphate,  as  is  pure  crude  petroleum,  the 
tannate  of  soda  and  other  chemicals. 

"  The  effect  of  incrustation  and  of  deposits  of  various  kinds,  is 
to  enormously  reduce  the  conducting  power  of  heating  surfaces  ; 


684  HANDBOOK    ON    ENGINEERING. 

so  much  so,  that  the  power,  as  well  as  the  economic  efficiency  of 
a  boiler,  may  become  very  greatly  reduced  below  that  for  which  it 
is  rated,  and  the  supply  of  steam  furnished  by  it  may  become 
wholly  inadequate  to  the  requirements  of  the  case. 

"It  is  estimated  thaty1^  of  an  inch  (0.1(5  cm.)  thickness  of 
hard  '  scale  '  on  the  heating  surface  of  a  boiler  will  cause  a  waste 
of  nearly  one-eighth  of  its  efficiency,  and  the  waste  increases  as  the 
square  of  its  thickness.  The  boilers  of  steam  vessels  are 
peculiarly  liable  to  injury  from  this  cause  where  using  salt  water, 
and  the  introduction  of  the  surface  condenser  has  been  thus 
brought  about  as  a  remedy.  Land  boilers  are  subject  to  incrus- 
tation by  the  carbonate  and  other  salts  of  lime  and  by  the  deposit 
of  sand  or  mud  mechanically  suspended  in  the  feed-water. 

THE    TEMPERATURE    AND    PRESSURE    OF    SATURATED 

STEAM. 

The  accompanying  diagram  and  explanation,  taken  from  that 
excellent  publication,  The  Locomotive ,  will  be  found  much  more 
convenient  for  reference  than  steam  tables.  The  description  says 
that  one  of  the  most  fundamental  and  best  known  facts  in  steam 
engineering  is  that  saturated  steam  has  a  certain  definite  tem- 
perature for  each  and  every  definite  pressure ;  and  in  all  books 
on  steam  we  find  tables  of  corresponding  temperatures  and  pres- 
sures, by  the  use  of  which  we  are  enabled  to  find  out  what 
the  temperature  of  the  steam  is  when  we  know  what  the  pres- 
sure is,  and  vice  versa.  For  accurate  work  these  tables  are  all 
right ;  but  when  (as  is  usually  the  case)  we  do  not  need  to 
know  either  the  temperature  or  the  pressure  with  any  very 
great  precision,  a  diagram  which  presents  the  facts  directly  to 
the  eye  is  much  more  convenient.  Such  a  diagram  is  presented 
herewith.  On  the  left-hand  side  of  each  vertical  line  I  have 
marked  the  pressures,  and  on  the  right-hand  side  of  the  same 
lines  I  have  marked  the  corresponding  temperatures.  The  pres- 


HANDBOOK    ON    ENGINEERING. 


685 


— 235' 


45—  -  55—  _ 


40—1 


~  — 235*  ~  —330* 


35—  _«„•        85— _ 


30 


25  —  Z 


20—1 


10 


100— i 

Zis    -- 


-2SO 

-275* 
-270* 

-265' 


-  — J25' 


80  — 


70— 


—  —250'        65— 


240* 


60 


_|_Z25.        55-i. 


E-2/5*        ?is    -_ 
^-2/2°         50—" 


J5* 


'45— 


/40— 


-I— 320'       /25— 


J/5* 


-—310' 


-—305* 


300' 


tzo— 


US 


HO 


105  — 


Us  - 
100  — 


—  360' 


/30  — 


185— 


175— 


—350' 


—  J45* 


165  — 


160  — 


155  — 


—340* 


—380' 


•370' 


COMPARATIVE  DIAGRAM    SHOWING   THE   TEMPERATURE  AND    PRESSURE 
OF   SATURATED   STEAM. 


68  fi  HANDBOOK    ON    ENGINEERING. 

sures  are  all  gauge  pressures,  that  is,  they  represent  the  direct 
gauge  reading  or  pressure  above  that  of  the  atmosphere.  The 
temperatures  are  on  the  Fahrenheit  scale.  The  diagram  is  based 
upon  Prof.  Cecil  H.  Peabody's  steam  tables,  and  we  have 
assumed  that  the  average  atmospheric  pressure  is  14.70  pounds 
per  square  inch. 

A  few  examples  will  make  the  use  of  the  diagram  clear:  (1) 
What  is  the  temperature  of  saturated  steam  when  its  pressure, 
above  the  atmosphere,  is  75  pounds  per  square  inch?  Ans.  We 
find  75  pounds  on  the  left-hand  side  of  the  second  vertical  line, 
and  looking  on  the  other  side  of  the  line  we  see  that  the  corre- 
sponding temperature  is  just  a  fraction  of  a  degree  less  than  320 
degrees  Fahr.  (2)  What  is  the  temperature  of  saturated  steam 
when  its  pressure,  above  the  atmosphere,  is  197  Ibs.  per  square 
inch?  Ans.  We  find  197  Ibs.  on  the  left-hand  side  of  the  last 
vertical  line.  It  is  not  marked  in  figures,  but  195  is  so  marked, 
and  197  is  two  divisions  higher  than  195.  Looking  opposite  to 
197  we  see  that  the  corresponding  temperature  is  about  half  way 
between  386  degrees  and  387  degrees.  Hence,  we  conclude  that 
the  temperature  of  saturated  steam  at  the  given  pressure  is  about 
386  J°.  (3)  When  the  temperature  of  saturated  steam  is  227°, 
what  is  its  pressure?  Ans.  We  find  227°  on  the  right-hand 
side  of  the  first  line,  two  divisions  above  225° ;  and  looking 
opposite  to  it,  we  see  that  the  gauge  pressure  corresponding  to 
this  temperature  is  almost  exactly  five  pounds.  (4)  When  the 
temperature  of  saturated  steam  is  363°,  what  is  its  pressure? 
Ans.  We  find  363°  on  the  right-hand  side  of  the  third  vertical 
line,  three  divisions  above  360°,  and  looking  on  the  other  side  of 
the  vertical  line,  we  see  that  the  corresponding  gauge  pressure  is 
about  144i  Ibs.  to  the  square  inch. 

SOMETHING   FOR  NOTHING. 

In  the  first  place,  it  should  be  remembered  that  in  mechanics 
the  measure  of  work  done  is  the  foot  pound,  a  term  which  defines 


HANDBOOK   ON    ENGINEERING. 


687 


itself.  A  foot  pound  of  work  is  the  amount  of  energy  required  to 
lift  one  pound  one  foot  high.  A  foot  pound,  therefore,  is  the 
product  of  force  and  distance,  force  being  simply  a  push  or  a 
pull.  A  machine  can  be  made  to  increase  the  acting  force,  as 
is  seen  in  the  case  of  a  crane,  where  the  weight  lifted  is  much 
greater  than  the  force  applied  at  the  handle  by  the  operator.  It 
is  also  possible  to  increase  the  distance  moved  by  some  part  of  a 
machine,  but  it  must  be  done  by  applying  a  greater  force  as  in 
the  case  of  a  steam  engine,  where  the  distance  moved  by  the  belt 
is  greater  than  the  space  passed  over  by  the  piston,  but  the  total 
pressure  of  the  steam  against  the  piston  is  greater  than  the 
effective  pull  exerted  by  the  belt. 


Melting  Points  of  Metals  and  Solids. 


Antimony  melts  at 

Bismuth  " 

Brass  " 

Cadmium  u 

Cast  Iron  " 

Copper  " 

Glass  " 

Gold  " 

Lead  " 

Ice  " 


Deg. 

Fahr.  j 

Deg.  Fahr. 

. 

.     951 

Platinum  melts  at     . 

. 

4580 

. 

.     476 

Potassium     " 

. 

135 

. 

.  1900 

Saltpeter       " 

. 

600 

.     , 

.     602 

Steel              " 

2340  to 

2520 

1890  to  2160 

Sulphur                    .  . 

. 

225 

. 

.  1890 

Silver             " 

. 

1250 

?"'•-•• 

.  2377 

Tin                 " 

. 

420 

. 

.  2250 

Wrought  Iron 

2700  to 

2880 

. 

.     594 

Zinc               " 

. 

740 

.     . 

.       32 

Aluminum     " 

.     .     . 

1260. 

In  both  the  crane  and  the  steam  engine,  however,  the  applied 
force  multiplied  by  the  distance  through  which  it  moves  in  a  given 
time,  must  be  enough  greater  than  the  product  of  the  force  at  the 
crane  hook  or  the  rim  of  the  fly-wheel,  and  the  distance  through 


688  HANDBOOK    ON    ENGINEERING. 

which  it  moves  to  make  up  for  the  loss  through  friction  in  the 
machine  itself.  The  foot  pounds  of  work  done  by  any  machine 
whatever  must  always  be  less  than  the  foot  pounds  put  into  the 
machine  in  the  same  length  of  time.  A  study  of  this  principle 
and  of  the  methods  of  applying  it,  is  all  that  is  necessary  to 
enable  one  to  decide  upon  the  soundness  of  the  claims  made  for 
any  power  multiplying  device.  A  British  Thermal  Unit  (B.  T. 
U.)  is  the  amount  of  heat  required  to  raise  the  temperature  of  a 
pound  of  water  1°  Fahr.,  and  its  dynamic  value  is  778  Ibs.  raised 
to  a  height  of  one  foot. 

CHIMNEYS. 

Chimneys  are  required  for  two  purposes :  1st,  to  carry  off 
obnoxious  gases;  2d,  to  produce  a  draft,  and  so  facilitate  com- 
bustion. The  first  requires  size,  the  second  height.  Each  pound 
of  coal  burned  yields  from  13  to  30  pounds  of  gas,  the  volume  of 
which  varies  with  the  temperature.  The  weight  of  gas  to  be  car- 
ried off  by  a  chimney,  in  a  given  time,  depends  on  three  things  — 
size  of  chimney,  velocity  of  flow  and  density  of  gas.  But  as  the 
density  decreases  directly  as  the  absolute  temperature,  while  the 
velocity  increases  with  a  given  height,  nearly  as  the  square  root 
of  the  temperature,  it  follows  that  there  is  a  temperature  at  which 
the  weight  of  gas  delivered  is  a  maximum.  This  is  about  550° 
above  the  surrounding  air.  Temperature,  however,  makes  so 
little  difference  that  at  550°  above  the  quantity  is  only  4  per  cent 
greater  than  at  300°.  Therefore,  height  and  area  are  the  only 
elements  necessary  to  consider  in  an  ordinary  chimney.  The  in- 
tensity of  draft  is,  however,  independent  of  the  size,  and  depends 
upon  the  difference  in  weight  of  the  outside  and  inside  columns  of 
air,  which  varies  nearly  as  the  product  of  the  height  into  the 
difference  of  temperature.  This  is  usually  stated  in  an  equiva- 
lent column  of  water,  and  may  vary  from  0  to  possibly  2  inches. 
After  a  height  has  been  reached  to  produce  draft  of  sufficient 


HANDBOOK    ON    ENGINEERING, 


689 


i    - 


692 


HANDBOOK    ON    ENGINEERING. 


the  diameter  of  the  stack  increases,  the  friction  in  stack  and 
breeching  decreases  rapidly.  Therefore,  for  the  third  and  each 
succeeding  boiler,  50  per  cent  of  the  first  area  will  suffice.  But 
as  more  are  added,  the  height  should  be  increased,  more  espe- 
cially if  the  horizontal  flue  from  boiler  to  stack  increases  in  length, 
as  it  usually  will.  A  good  rule  is  to  make  the  height  25  times 
the  diameter,  with  possibly  a  gradual  decrease  in  the  ratio  to  20 
times  the  diameter  for  the  larger  chimneys.  Thus  a  4-foot  diame- 
ter would  call  for  100-feet  height,  and  a  5-foot,  for  120-feet,  a 
6-foot  for  140-feet,  and  a  10-foot  for  200-feet  height. 


TABLE    OF    SIZES    OF    CHIMNEYS. 


I 

o> 

w 

Diameter  and  Nominal  Horse  Power. 

20" 

26" 

30" 

34" 

36" 

40" 

44" 

50" 

54" 

58" 

60" 

64" 

72" 

78" 

70ft. 

80ft. 
90ft. 
100  ft. 
110ft. 
120  ft. 

40 
50 

60 
75 

100 
120 

130 
150 

150 
175 

175 

200 

200 
225 
250 

300 
340 
360 

375 
400 
425 

430 
455 
500 

500 
550 
600 

600 
650 
700 

750 
825 
900 

930 
990 
1050 

IRON   CHIMNEY  STACKS. 

In  many  places  iron  stacks  are  preferred  to  brick  chimneys. 
Iron  chimneys  are  bolted  down  to  the  base  so  as  to  require  no 
stays.  A  good  method  of  securing  such  bolts  to  the  stack  is 
shown  in  detail  in  the  figure  on  page  693.  Iron  stacks  require  to  be 
kept  well  painted  to  prevent  rust,  and  generally,  where  not  bolted 
down,  as  here  shown,  they  need  to  be  braced  by  rods  or  wires  to 
surrounding  objects.  With  four  such  braces  attached  to  an 
angle  iron  ring  at  f  the  height  of  stack,  and  spreading  laterally  at 


HANDBOOK    ON    ENGINEERING. 

least  an  equal  distance,  each  brace  should  have  an  area  in  square 
inches  equal  to  TQ^Q-  the  exposed  area  of  stack  (dia.  x  height)  in 
feet.  Stability  or  power  to  withstand  the  overturning  force  of 


Holding  down  Bolts  and   Lugs. 

the  highest  winds,  requires  a  proportionate  relation  between  the 
weight,  height,  breadth  of  base,  and  exposed  area  of  the  chimney. 
This  relation  is  expressed  in  the  equation 


in  which    d  equals    the    average  breadth  of  the  shaft ;  h  =  its 
height ;  b  =  the  breadth  of   base  —  all   in  feet ;    W  ==  weight  of 
IN  LBS.,    and  C  =  a  coefficient   of   wind  pressure    per 


o 
CHIMNEY 


694 


HANDBOOK    ON    ENGINEERING. 


square  foot  of  area.  This  varies  with  the  cross-section  of  the 
chimney,  and  =  56  for  a  square,  35  for  an  octagon  and  28  for  a 
round  chimney.  Thus  a  square  chimney  of  average  breadth  of 
8  feet,  10  feet  wide  at  base  and  100  feet  high,  would  require  to 
weigh  56x8x100x10=448.000  Ibs.,  to  withstand  any  gale 
likely  to  be  experienced.  Brickwork  weighs  from  100  to  130 
Ibs.  per  cubic  foot;  hence,  such  a  chimney  must  average  13 
inches  thick  to  be  safe.  A  round  stack  could  weigh  half  as 
much,  or  have  less  base. 


WEIGHT      OF      SHEET      LAP      RIVETED      STEEL      SMOKE      STACKS, 
PER    FOOT, 

THICKNESS. 


DIA. 

No. 

18 

No. 
16 

No. 

14 

No. 

12 

No. 

10 

NTo. 
8 

A" 

*Y' 

1" 

4 

-3y 

A" 

ti" 

1" 

W 

*• 

H" 

1" 

12" 
14" 

8 
94 

10 
11* 

13 

154 

17 
20 

21 
24* 

291 

314. 
36} 

37 
42 

42 

48* 

47 

84  i 

52* 
62i 

58 
67 

63 
73* 

68} 

79} 

73* 
85 

78} 
91 

84 
97 

16" 

ioj 

13 

17* 

23 

28 

34 

42 

49 

56 

63 

70 

77 

84 

91 

98 

105 

112 

18" 

14* 

19} 

26 

31* 

38} 

47 

55 

63 

71 

79 

86 

94 

102 

110 

118 

126 

20" 

13* 

16 

22 

2;} 

35 

4-2* 

52 

60 

69 

78 

86 

95 

104 

113 

121 

131 

138 

22" 

1*4 

24  i 

31* 

38* 

46J 

54 

6:5* 

73 

82 

91 

99 

108 

118 

137 

146 

24" 

15* 

19* 

26* 

34} 

42 

51 

59 

68* 

78* 

88 

98 

108 

118 

128 

137 

147 

157 

26" 

16* 

21 

28J 

37 

45* 

551 

63 

73* 

84 

94 

105 

115 

126 

137 

147 

158 

Ifi8 

28" 

18 

22* 

31 

40 

49 

59* 

67 

78 

891 

100 

111 

122 

134 

145 

156 

167 

179 

20" 
32" 

| 

33 
35 

45* 

52* 
56 

68 

71 
75 

83i 

95" 
100* 

106* 
113 

118 
125 

130 
138 

142 

150 

154 
163 

166 
175 

178 
188 

190 

•201 

34" 

28 

37 

48} 

59* 

72i 

80 

93* 

106 

119 

132 

146 

160 

173 

186 

199 

21-2 

36" 

29* 

39 

51 

63 

764 

85 

100 

114 

128 

143 

158 

173 

188 

202 

216 

230 

38" 

*  " 

31* 

*14 

531 

66* 

801 

90 

105 

120 

135 

151 

166 

182 

1.98 

213 

227 

242 

40" 

83| 

43* 

56* 

70 

85 

94 

110 

126 

142 

158 

174 

191 

208 

224 

239 

254 

42" 

35 

45} 

59* 

73i 

89} 

98 

115 

132 

149 

166 

183 

200 

217 

234 

250 

266 

44" 

36} 

48 

62 

77" 

93* 

103 

121 

138 

155 

173 

191 

209 

227 

245 

262 

279 

48" 

38* 

50} 

65 

80* 

971 

107 

126 

144 

162 

181 

199 

218 

237 

255 

273 

291 

48" 

40 

524 

68 

84 

102 

112 

131 

150 

169 

188 

208 

227 

247 

266 

284 

303 

50" 

54f 

71 

871 

106} 

116 

136 

156 

176 

195 

216 

236 

258 

277 

296 

315 

52" 

57 

74 

91 

110* 

121 

142 

162 

182 

203 

224 

'245 

266 

287 

307 

3'28 

54" 

77 

94* 

124 

147 

168 

189 

211 

233 

254 

276 

298 

319 

349 

58" 

80 

98 

119 

133 

158 

180 

202 

225 

248 

270 

294 

317 

340 

363 

68" 

83 

102 

1231 

137 

164 

186 

209 

232 

256 

280 

304 

327 

351 

375 

60" 

86 

106 

127* 

142 

169 

192 

215 

240 

264 

289 

314 

338 

362 

387 

62" 

89 

110 

1311 

146 

174 

198 

222 

247 

273 

298 

324 

349 

374 

400 

64" 

92 

114 

136 

151 

179 

204 

229 

255 

281 

307 

333 

359 

385 

412 

HANDBOOK    ON    ENGINEERING.  695 

CHAPTER    XXIV. 
HORSE=POWER  OF  GEARS. 

To  determine  the  horse-power  which  any  gear-wheel  will  trans- 
mit, four  facts  are  required  to  be  known :  — 

1st.  The  kind  of  wheel,  whether  spur,  bevel,  spur  mortise,  or 
bevel  mortise.  2d.  The  pitch.  3d.  The  face.  4th.  The  velocity 
of  pitch  circle  in  feet  per  second. 

Generally,  the  fourth  fact  is  not  known.  It  can  be  found  if 
the  pitch  diameter  of  the  wheel  in  inches  and  the  number  of  revo- 
lutions per  minute  are  given,  for  it  can  be  obtained  from  them  by 
the  following  rule :  — 

Rule*  —  Given  the  pitch  diameter  in  inches  and  the  number  of 
revolutions  per  minute ;  to  find  the  velocity  of  pitch  line  in  feet 
per  second. 

First,  multiply  the  pitch  diameter  (in  inches)  by  the  number 
of  revolutions  per  minute.  Second,  divide  the  product  thus  found 
by  230.  The  quotient  i.s  the  velocity  required. 

Example. — What  is  the  velocity  of  the  pitch  circle  of  a 
gear-wheel  in  feet  per  second,  the  pitch  diameter  =  43  inches, 
the  revolutions  per  minute  =  125  ? 

43  x  125  divided  by  230  =  23.4  feet  per  second. 

Table  \  shows  the  greatest  horse-power  which  different  kinds 
of  gears  of  1-inch  pitch  and  1-inch  face  will  safely  transmit  at 
various  pitch-line  velocities.  To  find  the  greatest  horse-power 
which  any  other  pitch  and  face  will  safely  transmit,  the  following 
rule  can  be  used :  — 

Rule*  —  Given,  the  pitch  (in  inches),  face  (in  inches),  velocity 
of  pitch  circle  (in  feet  per  second) ,  and  kind  of  gear ;  to  find  the 
greatest  horse-power  that  can  be  safely  transmitted. 

First.  Find  the  horse-power  in  Table  2,  which  the  given  kind 


696 


HANDBOOK    ON     ENGINEERING. 


of  wheel  with  1-inch  pitch  and  1-inch  face  will  transmit  at  the 
given  velocity.  Second.  Multiply  the  pitch  by  the  face.  Third. 
Multiply  the  horse-power  found  by  the  product  of  pitch  by  face. 
The  final  product  is  the  horse-power  required. 

Example.  —  What  is  the  greatest  horse-power  that  a  bevel- 
wheel,  43"  pitch  diameter,  2"  pitch,  6"  face,  and  125  revolutions' 
per  minute  will  safely  transmit? 

From  previous  example,  we  have  found  the  pitch-line  velocity 
to  be  23.4  feet  per  second,  which  is  nearest  to  a  velocity  of  24 
feet  per  second  in  Table  1. 

First,  the  horse-power  which  a  bevel  wheel  of  1"  pitch  and  1' 
face  will  transmit  is. (from  table)  at  this  velocity  4.931. 

Second,  the  product  of  pitch  by  face  is  2x6  =  12. 

Third,  12  x  4. 931  =-59.17  horse-power.     Answer. 

Whenever  it  is  desirable  to  know  about  the  average  horse- 
power that  any  wheel  will  transmit,  |  or  *  of  the  results  obtained 
by  the  rule  above  should  be  taken. 

TABLE  1. — TABLE  SHOWING  THE  HORSE-POWER  WHICH  DIFFERENI 
KINDS  OF  GEAR  WHEELS  OF  ONE  INCH  PITCH  AND  ONE  INCH  FACE 
WILL  TRANSMIT  AT  VARIOUS  VELOCITIES  OF  PITCH  CIRCLE. 


1 

2 

3 

4 

5 

Velocity  of 
pitch  circle  in 
ft.  per  sec. 

Spur  Wheels. 

Spur  Mortise 
Wheels. 

Bevel  Wheels. 

Bevel 
Mortise 
Wheels. 

2 

1.338 

.047 

.938 

.647 

3 

1.756 

.971 

1.227 

.856 

6 

2.782 

1.76 

1.76 

1  363 

12 

4.43 

3.1 

3.1 

2.16 

18 

5.793 

4.058 

4.058 

2.847 

24 

7.052 

4.931 

4.931 

3.447 

30 

8.182 

5.727 

5.727 

4.036 

36 

9.163 

6.314 

6.414 

4.516 

42 

10.156 

7.102 

7  .  102 

4.963 

48 

10.083 

7.680 

7.680 

5.411 

HANDBOOK    ON    ENGINEERING. 


NOTE.  —  When  velocities  are  given,  which  are  between  these 
in  Table,  the  horse-power  can  be  found  by  interpolation. 

Thus,  the  horse-power  for  spur  wheels  at  14  feet  velocity  is 
found  as  follows  :  — 

14  minus  12  =  21    5.793  minus  4.43  =  1.363. 
18       "      12  =  6  J 

Then  |  of  1.363  =  .454  and  .454  -f  4.43  =  4. 884  horse-power. 

TABLE  2. — SHAFTING,  —  HORSE- POWER  TRANSMITTED  BY  VARIOUS 
SHAFTS,  AT  100  REVOLUTIONS  PER  MINUTE  UNDER  VARIOUS  CON- 
DITIONS. 


1 

2 

3 

4 

1 

2 

3 

4 

Shafts 

Shafts 

Diameter 
of  Shaft. 

Line 
Shafts. 

Shaft  as 
a  Prime 
Mover. 

Under 
Slight 
Bending 

Diameter 
of  Shaft. 

Line 
Shafts. 

Shaft  as 
a  Prime 
Mover. 

Under 
Slight 
Bending 

Strain. 

Strain. 

& 

.7 

.4 

1.3 

3H 

40. 

20. 

80- 

w 

1.3 

.7 

2.6 

3{f 

49. 

25. 

97. 

1-Z_ 

2.4 

1.2 

4.7 

4^ 

70. 

35. 

139. 

]JJL 

.3.8 

1.9 

7.6 

4f& 

96. 

48. 

192. 

1  JL| 

5.8 

2.9 

11.5 

5- 

K 

126. 

64. 

256. 

9-1- 

8.3 

4.2 

16.6 

5J 

Lf 

167. 

84. 

334. 

»ft 

11.5 

5.8 

23. 

e- 

L^ 

266. 

133. 

532. 

2fl 

15.5 

7.8 

31. 

7J 

L^ 

399. 

200. 

797. 

•tt 

20. 

10. 

40. 

8J 

570. 

285. 

1139. 

3ft 
4 

26. 
33. 

13. 

17. 

51. 
65. 

9 

1 

783. 

392. 

1566. 

This  table  states  the  horse-power  that  various  sizes  of  shafts 
will  safely  transmit  at  100  revolutions  per  minute  under  various 
conditions. 

Prime  movers  are  those  shafts  in  which  the  variation  above 
and  below  the  average  horse-power  transmitted  is  great,  also 
where  the  transverse  strain  due  to  belts  or  heavy  pulleys  is  large, 
such  as  jack-shafts,  crank-shafts,  etc. 


696 


HANDBOOK    ON     ENGINEERING. 


of  wheel  with  1-inch  pitch  and  1-inch  face  will  transmit  at  the 
given  velocity.  Second.  Multiply  the  pitch  by  the  face.  Third. 
Multiply  the  horse-power  found  by  the  product  of  pitch  by  face. 
The  final  product  is  the  horse-power  required. 

Example. —  What  is  the  greatest  horse-power  that  a  bevel- 
wheel,  43"  pitch  diameter,  2"  pitch,  6"  face,  and  125  revolutions' 
per  minute  will  safely  transmit? 

From  previous  example,  we  have  found  the  pitch-line  velocity 
to  be  23.4  feet  per  second,  which  is  nearest  to  a  velocity  of  24 
feet  per  second  in  Table  1. 

First,  the  horse-power  which  a  bevel  wheel  of  1"  pitch  and  1' 
face  will  transmit  is  (from  table)  at  this  velocity  4.931. 

Second,  the  product  of  pitch  by  face  is  2  x  6  =  12. 

Third,  12  x  4.931  —  59. 17  horse-power.     Answer. 

Whenever  it  is  desirable  to  know  about  the  average  horse- 
power that  any  wheel  will  transmit,  |  or  J  of  the  results  obtained 
by  the  rule  above  should  be  taken. 

TABLE  1.— TABLE  SHOWING  THE  HORSE-POWER  WHICH  DIFFERENT 
KINDS  OF  GEAR  WHEELS  OF  ONE  INCH  PITCH  AND  ONE  INCH  FACE 
WILL  TRANSMIT  AT  VARIOUS  VELOCITIES  OF  PITCH  CIRCLE. 


1 

2 

3 

4 

5 

Velocity  of 
pitch  circle  in 
ft.  per  sec. 

Spur  Wheels. 

Spur  Mortise 
Wheels. 

Bevel  Wheels. 

Bevel 
Mortise 
Wheels. 

2 

1.338 

.047 

.938 

.647 

3 

1.756 

.971 

1.227 

.856 

6 

2.782 

1.76 

1.76 

1  363 

12 

4.43 

3.1 

3.1 

2.16 

18 

5.793 

4.058 

4.058 

2.847 

21 

7.052 

4.931 

4.931 

3.447 

30 

8.182 

5.727 

5.727 

4.036 

36 

9.1G3 

6.314 

6.414 

4.516 

42 

10.156 

7.102 

7  .  102 

4.963 

48 

10.083 

7.680 

7.680 

5.411 

HANDBOOK    ON    ENGINEERING. 


NOTE.  —  When  velocities  are  given,  which  are  between  these 
in  Table,  the  horse-power  can  be  found  by  interpolation. 

Thus,  the  horse-power  for  spur  wheels  at  14  feet  velocity  is 
found  as  follows :  — 

14  minus  12  =  2  j  minus  4.48=  ^gg. 

18       "      12  =  6  J 

Then  f  of  1.363  =  .454  and  .454  -j-  4.43  —  4.884  horse-power. 

TABLE  2.  — SHAFTING.  —  HORSE- POWER  TRANSMITTED  BY  VARIOUS 
SHAFTS,  AT  100  REVOLUTIONS  PER  MINUTE  UNDER  VARIOUS  CON- 
DITIONS. 


1 

2 

3 

4 

1 

2 

3 

4 

Shafts 

Shafts 

Diameter 
of  Shaft. 

Line 
Shafts. 

Shaft  as 
a  Prime 
Mover. 

Under 
Slight 
Bending 

Diameter 
of  Shaft. 

Line 
Shafts. 

Shaft  as 
a  Prime 
Mover. 

Under 
Slight 
Bending 

Strain. 

Strain. 

if 

.7 

.4 

1.3 

W 

40. 

20. 

80- 

w 

1.3 

.7 

2.6 

sir 

49. 

25. 

97. 

2.4 

1.2 

4.7 

W' 

70. 

35. 

139. 

1  4"-^' 

.3.8 

1.9 

7.6 

4ffc" 

96. 

48. 

192. 

1  JL|/ 

5.8 

2.9 

11.5 

5- 

V 

126. 

64. 

256. 

-iV 

8.3 

4.2 

16.6 

5J 

Lf" 

167. 

84. 

334. 

2-j2g/ 

11.5 

5.8 

23. 

£ 

••§•" 

266. 

133. 

532. 

2tt' 

15.5 

7.8 

31. 

7J 

t" 

399. 

200. 

797. 

2f  «' 

20. 

10. 

40. 

8J 

t" 

570. 

285. 

1139. 

w 

26. 

13. 

51. 

9 

r 

783. 

392. 

1566. 

33. 

17. 

65. 

This  table  states  the  horse-power  that  various  sizes  of  shafts 
will  safely  transmit  at  100  revolutions  per  minute  under  various 
conditions. 

Prime  movers  are  those  shafts  in  which  the  variation  above 
and  below  the  average  horse-power  transmitted  is  great,  also 
where  the  transverse  strain  due  to  belts  or  heavy  pulleys  is  large, 
such  as  jack-shafts,  crank-shafts,  etc. 


698  •      HANDBOOK    ON    ENGINEERING. 

WHEEL  GEARING. 

The  pitch  line  of  a  wheel  is  the  circle  upon  which  the  pitch 
is  measured,  and  it  is  the  circumference  by  which  the  diameter, 
or  the  velocity  of  the  wheel,  is  measured.  The  pitch  is  the  arc 
of  the  circle  of  the  pitch  line,  and  is  determined  by  the  num- 
ber of  teeth  in  the  wheel.  The  true  pitch  (chordal),  or  that 
by  which  the  dimensions  of  the  tooth  of  a  wheel  are  alone 
determined,  is  a  straight  line  drawn  from  the  centers  of  two 
contiguous  teeth  upon  the  pitch  line.  The  line  of  centers  is 
the  line  between  the  centers  of  two  wheels.  The  radius  of  a 
wheel  is  the  semi-diameter  running  to  the  periphery  of  a  tooth. 
The  pitch  radius  is  the  semi-diameter  running  to  the  pitch  line. 
The  length  of  a  tooth  is  the  distance  from  its  base  to  its  ex- 
tremity. The  breadth  of  a  tooth  is  the  length  of  the  face  of 
wheel.  The  teeth  of  wheels  should  be  as  small  and  numerous 
as  is  consistent  with  strength.  When  a  pinion  is  driven  by 
a  wheel,  the  number  of  teeth  in  the  pinion  should  not  be 
less  than  eight.  When  a  wheel  is  driven  by  a  pinion,  the 
number  of  teeth  in  the  pinion  should  not  be  less  than  ten. 
The  number  of  teeth  in  a  wheel  should  always  be  prime  to  the 
number  of  the  pinion ;  that  is,  the  number  of  teeth  in  the 
wheel  should  not  be  divisible  by  the  number  of  teeth  in  the 
pinion,  without  a  remainder.  This  is  in  order  to  prevent  the 
same  teeth  coming  together  so  often  as  to  cause  an  irregular 
wear  of  their  faces.  An  odd  tooth  introduced  into  a  wheel  is 
termed  a  hunting-tooth  or  cog. 

TO    COMPUTE    THE    PITCH    OP    A    WHEEL. 

Rule*  —  Divide  the  circumference  at  the  pitch-line  by  the  num- 
ber of  teeth. 

Example.  —  Awheel  40  in.  in  diameter,  requires  75  teeth; 
what  is  its  pitch  ? 

3.1416x40       ,  fir.K-  . 

=  1.6755  in. 

75 


HANDBOOK    ON    ENGINEERING.  699 

TO    COMPUTE    THE     CHORDAL    PITCH. 

Rule*  —  Divide  180°  by  the  number  of  teeth,  ascertain  the  sin. 
of  the  quotient,  and  multiply  it  by  the  diameter  of  the  wheel. 

•Example.  —  The  number  of  teeth  is   75  and  the   diameter  40 
in. ;  what  is  the  true  pitch  ? 
180 


75 


=  2°  24'  and  sin.  of  2°  24'  =  .04188,  which  x  40  =  1.6752  in. 


TO  COMPUTE  THE  DIAMETER  OF  A  WHEEL. 

Rule*  —  Multiply  the  number  of  teeth  by  the  pitch,  and  divide 
the  product  by  3.1416. 

Example. — The  number   of   teeth  in   awheel  is  75,  and  the 
pitch  1.675  in.  ;  what  is  the  diameter  of  it? 
75x1.675 


3.1416 


—  40  in. 


TO    COMPUTE    THE    NUMBER    OF    TEETH    IN    A    WHEEL. 

—  Divide  the  circumference  by  the  pitch. 

TO  COMPUTE  THE    DIAMETER    WHEN  THE    TRUE  PITCH    IS    GIVEN. 

Rule.  —  Multiply  the  number  of  teeth  in  the  wheel  by  the  true 
pitch,  and  again  by  .3184. 

Example.  — Take  the  elements  of  the  preceding  case. 
75  x  1.6752  x  .3184  =  40  in. 

TO  COMPUTE    THE    NUMBER    OF  TEETH  IN  A    PINION    OR    FOLLOWER  TO 
HAVE    A    GIVEN   VELOCITY. 

Rule, —  Multiply  the  velocity  of  the  driver  by  its  number  of 
teeth,  and  divide  the  product  by  the  velocity  of  the  driven. 

Example. — The  velocity  of  a  driver  is  16  revolutions,  the 
number  of  its  teeth  54,  and  the  velocity  of  the  pinion  is  48  ;  what 
is  the  number  of  its  teeth  ? 

H£!4  =  18  teeth. 
48 


\ 
700  HANDBOOK    ON    ENGINEERING. 

2.  A  wheel  having  75  teeth  is  making  16  revolutions  per  min- 
ute. What  is  the  number  of  teeth  required  in  the  pinion  to  make 
24  revolutions  in  the  same  time  ? 


24 


TO    COMPUTE    THE    PROPORTIONAL    RADIUS  OF     A     WHEEL    OR  PINION. 

Rule* —  Multiply  the  length  of  the  line  of  centers  by  the  num- 
ber of  teeth  in  the  wheel  for  the  wheel,  and  in  the  pinion  for  the 
pinion,  and  divide  by  the  number  of  teeth  in  both  the  wheel  and 
the  pinion. 

TO  COMPUTE  THE  DIAMETER  OF  A  PINION,  WHEN  THE  DIAMETER  OF 
THE  WHEEL  AND  NUMBER  OF  TEETH  IN  THE  WHEEL  AND  PINION 
ARE  GIVEN. 

Rule*  —  Multiply  the  diameter  of  the  wheel  by  the  number  of 
teeth  in  the  pinion,  and  divide  the  product  by  the  number  of  teeth 
in  the  wheel. 

Example. — The  diameter  of  a  wheel  is  25  in.,  the  number  of 
its  teeth  210,  and  the  number  of  teeth  in  the  pinion  30 ;  what  is 
the  diameter  of  the  pinion  ?  • 
25x30 


210 


=  3.57  in. 


TO  COMPUTE  THE    CIRCUMFERENCE    CF  A  WHEEL. 

—  Multiply  the  number  of  teeth  by  their  pitch. 

TO  COMPUTE  THE  REVOLUTIONS  OF  A  WHEEL  OR  PINION. 


—  Multiply  the  diameter  or  circumference  of  the  wheel  or 
the  number  of  its  teeth,  as  the  case  may  be,  by  the  number  of  its 
revolutions,   and  divide  the  product  by  the  diameter,  circumfer- 
ence, or  number  of  teeth  in  the  pinion. 
•  Example.  —  A  pinion  10  in.  in  diameter  is  driven  by  a  wheel 


HANDBOOK    ON    ENGINEERING.  701 

2  ft.  in  diameter,  making  46  revolutions  per  minute  ;  what  is  the 
number  of  revolutions  of  the  pinion  ? 
2  x  12x46 


10 


—  110.4  revolutions. 


TO  COMPUTE  THE  VELOCITY  OF   A  PINION. 

Rule* — Divide  the  diameter,  circumference  or  number  of  teeth 
in  the  driver,  as  the  case  may  be.  by  the  diameter,  etc.,  of  the 
pinion. 

WHEN  THERE  IS  1.  SERIES  OR  TRAIN  OF  WHEELS  AND  PINIONS. 

Rule*  —  Divide  the  continued  product  of  the  diameter,  circum- 
ference, or  number  of  teeth  in  the  wheels  by  the  continued 
product  of  the  diameter,  etc.,  of  the  pinions. 

Example. — If  a  wheel  of  32  teeth  drive  a  pinion  of  10,  upon 
the  axis  of  which  there  is  one  of  30  teeth,  driving  a  pinion  of  8, 
what  are  the  revolutions  of  the  last  ? 
32     30       960 
K)X"8  ==  scT  =  =12  revolutions. 

Ex.  2.  — The  diameters  of  a  train  of  wheels  are  6,  9,  9,  10  and 
12  in. ;  of  the  pinions,  6,  6,  6,  6,  and  6  in.  ;  and  the  number  of 
revolutions  of  the  driving  shaft  or  prime  mover  is  10 ;  what  are 
the  revolutions  of  the  last  pinion  ? 

6  x  9  x  9  x  10  x  12  x  10       583200 

=. =_  tb  revolutions. 

6x6x6x6x6  7776 

TO  COMPUTE  THE  PROPORTION  THAT  THE  VELOCITIES  OF  THE  WHEELS 
IN  A  TRAIN  WOULD  BEAR  TO  ONE  ANOTHER. 

Rule*  —  Subtract  the  less  velocity  from  the  greater,  and  divide 
the  remainder  by  one  less  than  the  number  of  wheels  in  the  train ; 
the  quotient  is  the  number,  rising  in  arithmetical  progression  from 
the  less  to  the  greater  velocity. 


702  HANDBOOK    ON    ENGINEERING. 

Example.  —  What  should  be  the  velocities  of  three  wheels  to 
produce  18  revolutions,  the  driver  making  3? 
18  minus  3  =  15^  =  ^g  =  number  to  be  ftdded  to  velocity  of  the 
3  minus  1=2 

driver  =  7. 5  +  3  =  10. 5     and    10.5  -f-  7.5  =  18    revolutions. 
Hence,  3,  10.5  and  18  are  the  velocities  of  the  three  wheels. 

GENERAL    ILLUSTRATIONS. 

1.  A  wheel  96  inches   in  diameter,  having  42  revolutions  per 
minute,  is  to  drive  a  shaft  75  revolutions  per  minute,  what  should 
be  the  diameter  of  the  pinion  ? 

96x42 

_  =53.76  in. 
75 

2.  If  a  pinion  is  to  make  20  revolutions  per  minute,  required 
the  diameter  of  another  to  make  58  revolutions  in  the  same  time. 
58  divided  by   20  =  2.9  =  the  ratio  of  their  diameters.     Hence 
if  one  to  make  20   revolutions  is  given  a  diameter  of  30  in.,  the 
other  will  be  30  divided  by  2.9  =  10.345  in. 

3.  Required  the  diameter  of  a  pinion  to  make  12i  revolutions 
in  the  same  time  as  one  of*32  in.  diameter  making  26. 

32x26 

66.56  in. 
12.5 

4.  A  shaft  having  22  re  volutions  per  minute,  is  to  drive  another 
shaft  at  the  rate  of  15,  the  distance  between  the  two  shafts  upon 
the  line  of  centers  is  45  in.  ;  what  should  be  the  diameter  of  the 
wheels  ? 

Then,  1st,  22  -f-  15  :  22  :  :  45  :  26.75  =  inches  in  the  radius  of 
the  pinion. 

2d.   22  -f  15  :  15  :  :  45  :  18.24  =  inches  in  the  radius  of  the  spur. 

5.  A  driving   shaft,  having    16    revolutions   per  minute,  is  to 
drive  a  shaft  81  revolutions  per  minute,  the  motion  to  be   com- 
municated by  two  geared  wheels  and  two  pulleys,  with   an  inter- 
mediate shaft ;  the  driving  wheel  is  to  contain  54  teeth,  and  the 


HANDBOOK    ON    ENGINEERING.  703 

driving  pulley  upon  the  driven  shaft  is  to  be  25  in.  in  diameter ; 
required  the  number  of  teeth  in  the  driven  wheel,  and  the  diameter 
of  the  driven  pulley.  Let  the  driven  wheel  have  a  velocity  of 
V  16x81=36  a  mean  proportional  between  the  extreme  veloci- 
ties 16  and  81. 

Then,  1st,  36  :  16  :  :  54  :  24  =  teeth  in  the  driven  wheel. 

2d.  81 :  36  :  :  25  :  11.11  =  inches  diameter  of  the  driven  pulley. 

6.  If,  as  in  the  preceding  case,  the  whole  number  of  revolutions 
of  the  driving  shaft,  the  number  of  teeth  in  its  wheel  and  the 
diameter  of  the  pulley  are  given,  what  are  the  revolutions  of  the 
shafts? 

Then,  1st,  18  :  16  :  :  54  :  48  =  revolutions  of  the  intermediate 
shaft. 

2d.    15  :  48  :  :  25  :  80  =  revolutions  of  the  driven  shaft. 

TO     COMPUTE  THE    DIAMETER  OF    A  WHEEL  FOR  A  GIVEN    PITCH     AND 
NUMBER  OF  TEETH. 

Rule*  —  Multiply  the  diameter  in  the  following  table  for  the 
number  of  teeth  by  the  pitch,  and  the  product  will  give  the  diam- 
eter at  the  pitch  circle. 

Example. — What  is  the  diameter  of  a  wheel  to  contain  48 
teeth  of  2.5  in.  pitch? 

15.29x2.5  =  38.225  in. 

TO  COMPUTE    THE    PITCH    OF  A    WHEEL    FOR  A    GIVEN  DIAMETER    AND 
NUMBER    OF    TEETH. 

Rule*  —  Divide  the  diameter  of  the  wheel  by  the  diameter  in 
the  table  for  the  number  of  teeth,  and  the  quotient  will  give  the 
pitch. 

Example.  —  What  is  the  pitch  of  a  wheel  when  the  diameter  of 
it  is  50.94  in.,  and  the  number  of  its  teeth  80? 

50.94 


704 


HANDBOOK    ON    ENGINEERING. 


PITCH  OF  WHEELS. 

A    TABLE   WHEREBY    TO     COMPUTE     THE    DIAMETER    OF    A    WHEEL   FOR   A 
GIVEN     PITCH,    OH    THE    PITCH    FOR   A    GIVEN     DIAMETER. 

From  8  to  192  teeth. 


g 

03 

.c 

1 

^ 

1 

a 

1 

JS 

1 

"8  03 

S 

"o  o> 

I 

«M     - 

0  03 

i 

O  OJ 

I 

0  S 

S 

d^""1 

03 

6 

• 

6 

a 

d^"1 

45 

d 

I 

55 

5 

fe 

5 

* 

5 

fc 

5 

fc 

5 

8 

2.61 

45 

14.33 

82 

26.11 

119 

37.88 

156 

49.66 

9 

2.93 

46 

14.65 

83 

26.43 

120 

38.2 

157 

49.98 

10 

3.24 

47 

14.97 

84 

26.74 

121 

38.52 

158 

50.3 

11 

3.55 

48 

15.29 

85 

27.06 

122 

38.84 

159 

50.61 

12 

3.86 

49 

15.61 

86 

27.38 

123 

39.16 

160 

50.93 

13 

4.18 

50 

15.93 

87 

27.7 

124 

39.47 

161 

51.25 

14 

4.49 

51 

16.24 

88 

28.02 

125 

39.79 

162 

51.57 

15 

4.81 

52 

16.56 

89 

28.33 

126 

40.11 

163 

51.89 

16 

5.12 

53 

16.88 

90 

28.  H5 

127 

40.43 

164 

52.21 

17 

5.44 

54 

17.2 

91 

28.97 

128 

40.75 

165 

52.52 

18 

5.76 

55 

17.52 

92 

29.29 

129 

41.07 

166 

52.84 

19 

6.07 

56 

17.8 

93 

29.61 

130 

41.38 

167 

53.16 

20 

6.39 

57 

18.15 

94 

29.93 

131 

41.7 

168 

53.48 

21 

6.71 

58 

18.47 

95 

30.24 

132 

42.02 

169 

53.8 

22 

7.03 

59 

18.79 

9« 

30.56 

133 

42.34 

170 

54.12 

23 

7.34 

60 

19.11 

97 

30.88 

134 

42.66 

171 

54.43 

24 

7.66 

61 

19.42 

98 

31.2 

135 

42.98 

172 

54.75 

25 

7.98 

62 

19.74 

99 

31.52 

136 

43.29 

173 

55.07 

26 

8.3 

63 

20.06 

100 

31.84 

137 

43.61 

174 

55.39 

27 

8.61 

64 

20.38 

101 

32.15 

138 

43.93 

175 

55.71 

28 

8.93 

65 

20.7 

102 

32.47 

139 

44.25 

176 

56.02 

29 

9.25 

66 

21.02 

103 

32.79 

140 

44.57 

177 

56.34 

30 

9.57 

67 

21.33 

104 

33.11 

141 

44.88 

178 

56.66 

31 

9.88 

68 

21.65 

105 

33.43 

142 

45.2 

179 

56.98 

32 

10.2 

69 

21.97 

106 

33.74 

143 

45.52 

180 

57.23 

33 

10.52 

70 

22.29 

107 

34.06 

144 

45.84 

181 

57.62 

34 

10.84 

71 

22.61 

108 

34.38 

145 

46.16 

182 

57.93 

35 

11.16 

72 

22.92 

109 

34.7 

146 

46.48 

183 

58.25 

36 

11.47 

73 

23.24 

110 

35.02 

147 

46.79 

184 

58.57 

37 

11.79 

74 

23.56 

111 

35.34 

148 

47.11 

185 

58.89 

38 

12.11 

75 

23.88 

112 

35.65 

149 

47.43 

186 

59.21 

39 

12.43 

76 

24.2 

113 

35.97 

150 

47.75 

187 

59.53 

40 

12.74 

77 

24.52 

114 

36.29 

151 

48.07 

188 

59.84 

41 

13.06 

78 

24.83 

115 

36.61 

152 

48.39 

189 

60.16 

42 

13.38 

79 

25.15 

116 

36.93 

153 

48.7 

190 

60.48 

43 

13.7 

80 

25.47 

117 

37.25 

154 

49.02 

191 

60.81 

44 

14.02 

81 

25.79 

118 

37.56 

155 

49.34 

192 

61.13 

HANDBOOK    ON    ENGINEERING. 


705 


TO    COMPUTE    THE    STRESS    THAT    MAY    BE    BORNE    BY    A  TOOTH. 

Rule*  —  Multiply  the  value  of  the  material  of  the  tooth  to  re- 
sist transverse  strain,  as  estimated  for  this  character  of  stress,  by 
the  breadth  and  square  of  its  depth,  and  divide  the  product  by 
the  extreme  length  of  it  in  the  decimal  of  a  foot. 

TO    COMPUTE    THE     NUMBER     OF     TEETH      OF    A    WHEEL    FOR    -A.    GIVEN 
DIAMETER    AND    PITCH. 

Rule*  —  Divide  the  diameter  by  the  pitch ,  and  opposite  to  the 
quotient  in  the  preceding  table  is  given  the  number  of  teeth. 

TEETH  OP  WHEELS. 

Epicycloidal*  —  In  order  that  the  teeth  of  the  wheels  and  pin- 
ions should  work  evenly  and  without  unnecessary  rubbing  fric- 
tion, the  face  (from  pitch  line  to  top)  of  the  outline  should  be 
determined  by  an  epicycloidal  curve,  and  the  flank  (from  pitch 
line  to  base)  by  an  hypocycloidal.  When  the  generating  circle  is 
equal  to  half  the  diameter  of  the  pitch  circle,  the  hypocycloid  de- 
scribed by  it  is  a  straight  diametrical  line,  and  consequently  the 
outline  of  a  flank  is  a  right  line  and  radial  to  the  center  of  the 
wheel.  If  a  like  generating  circle  is  used  to  describe  face  of  a 
tooth  of  other  wheel  or  pinion  respectively,  the  wheel  and  pinion 
will  operate  evenly. 

Involute*  —  Teeth  of  two  wheels  will  work  truly  together  when 
surfaces  of  their  face  is  an  involute ;  and  that  two  such  wheels 
should  work  truly,  the  circles  from  which  the  involute  lines  for 
each  wheel  are  generated  must  be  concentric  with  the  wheels, 
with  diameters  in  the  same  ratio  as  those  of  the  wheels. 

Curves  of  teeth*  —  In  the  pattern  shop,  the  curves  of  epicy- 
cloidal or  involute  teeth  are  defined  by  rolling  a  template  of  the 
generating  circle  on  a  template  corresponding  to  the  pitch  line, 

a  scriber  on  the  periphery  of  the  template  being  used   to  define 

45 


706 


HANDBOOK    ON    ENGINEERING. 


the  curve.  Least  number  of  teeth  that  can  be  employed  in  pin- 
ions having  teeth  of  following  classes,  are :  involute,  25 ; 
epicycloidal,  12  ;  staves  or  pins,  6. 


CONSTRUCTION  OF  GEARING. 

If  the  dimensions  of  two  wheels  are  determined,  as  well  as 
the  size  of  the  teeth  and  spaces,  the  wheel  is  drawn  as  shown 
in  figure.  The  starting- 
point  for  the  division  of 
the  wheels  is  where  the 
two  pitch  circles  meet 
in  A.  It  is  advisable 
to  determine  the  exact 
diameters  of  the  wheels 
by  calculation,  if  the 
difference  between 
them  is  remarkable  ;  for 
any  division  upon  two 
circles  of  unequal  size 
by  means  of  a  divider, 
is  incorrect,  because  the  latter  measures  the  chord  instead  of  the 
arc.  From  the  point  A  we  construct  the  epicycloid  (7,  by  rolling 
the  circle  A  upon  JB,  as  its  base  line.  That  short  piece  of  the  epi- 
cycloid, from  the  pitch  line  to  the  face  of  the  tooth,  is  the  curva- 
ture for  that  part  of  the  tooth  and  the  wheel  B.  This  curvature 
obtained  for  one  side  of  the  tooth,  serves  for  both  sides  of  it,  and 
also  for  all  the  teeth  in  the  wheel.  The  lower  part  of  the  tooth, 
or  that  inside  the  pitch-line,  is  immaterial  to  the  working  of  the 
wheel;  this  may  be  a  straight  line,  as  shown  by  the  dotted  lines 
which  are  in  the  direction  of  the  diameters,  or  may  be  a  curved 
line,  as  is  seen  in  the  wheel  A.  This  line  must  be  so  formed  as 
not  to  touch  the  upper  or  curved  part  of  the  tooth.  The  root  of 


HANDBOOK    ON    ENGINEERING. 


707 


the  tooth,  or  that  part  of  it  which  is  connected  with  the  rim  of  the 
wheel,  is  the  weakest  part  of  the  tooth,  and  may  be  strengthened 
by  filling  the  angles  at  the  corners.  The  curvature  for  the  teeth 
in  the  wheel  A  is  found  in  a  similar  manner  to  that  of  B.  The 
pitch  circle  A  serves  now  as  a  base  line,  and  the  circle  B  is  rolled 
upon  it,  to  obtain  the  circle  D.  This  line  forms  the  curvature  for 
the  teeth  of  J.,  and  serves  for  all  the  teeth  in  A  —  also  for  both 
sides  of  the  teeth.  In  most  practical  cases  the  curvature  of  the 
teeth  is  described  as  a  part  of  a  circle,  drawn  from  the  center  of 
the  next  tooth,  or  from  a  point  more  or  less  above  or  below  that 
center,  or  the  radius  greater  or  less  in  strength  than  the  pitch  of 
the  wheel.  Such  circles  are  never  correct  curves,  and  no  rule  can 
be  established  by  which  their  size  and  center  meets  the  form  of 
the  epicycloid. 

BEVEL    WHEELS. 

If  the  lines  C  A  and  B  C  represent  the  prolonged  axes,  which 
are  to  revolve  with  different  or  similar  velocities,  the  position  and 

sizes  of  the  wheels  for 
driving  these  axes  are 
determined  by  the  dis- 
tance of  the  wheels  from 
the  point  C.  The  diame- 
ters of  the  wheels  are  as 
the  angles  a  and  b  and 
inversely  as  the  number 
of  revolutions.  These 
angles  are,  therefore,  to 

D  be  determined  before  the 

wheels  can  be  drawn.' 
By  measuring  the  distances  from  C  to  the  line  E,  or  from  C  to 
-F,  the  sizes  of  the  wheels  are  determined.  These  lines  E,  F  and 
D  jP,  are  the  diameters  for  the  pitch  lines ;  from  them  the  form 


708 


HANDBOOK    ON    ENGINEERING. 


of  the  tooth  is  described  on  the  beveled  face  of  the  wheel.  If 
the  form  of  the  tooth  is  described  on  the  largest  circle  of  the 
wheel,  all  the  lines  from  this  face  run  to  the  point  O,  so  that  when 
the  wheel  revolves  around  its  axis,  all  the  lines  from  the  teeth 
concentrate  in  the  point  (7,  and  form  a  perfect  cone.  Curvature, 
thickness,  length  and  spaces  are  here  calculated  as  on  face 
wheels ;  the  thickness  is  measured  in  the  middle  of  the  width  of 

the  wheel. 

WORM-SCREW. 

If  a  single  screw  A  works  in  a  toothed  wheel,  each  revolution 
of  the  screw  will  turn  the  wheel  one  cog  ;  if  the  screw  is  formed 
of  more  than  one  thread,  a  corresponding  number  of  teeth  will  be 
moved  by  each  revolution. 
With  the  increase  of  the 
number  of  threads,  the  side 
motion  of  the  wheel  and 
screw  is  accelerated ;  and 
when  the  threads  and  num- 
ber of  teeth  are  equal, an 
angle  of  45°  is  required  for 
teeth  and  thread,  provided 
their  diameters  also  are 
equal.  This  motion  causes 
a  great  deal  of  friction  and 
it  is  only  resorted  to  where  no  other  means  can  be  employed  to 
produce  the  required  motion.  In  small  machinery,  the  worm  is 
frequently  made  use  of  to  produce  a  uniform,  uninterrupted 
motion ;  the  screw,  in  such  cases,  is  made  of  hardened  steel  and 
the  teeth  of  the.  wheel  are  cut  by  the  screw  which  is  to  work  in 
the  wheel.  If  the  form  of  the  teeth  in  the  wheel  is  not  curved 
and  its  face  is  concave  so  as  to  fit  the  thread  in  all  points,  the 
screw  will  touch  the  teeth  but  in  one  point  and  cause  them  to  be 
liable  to  breakage, 


HANDBOOK    ON    ENGINEERING.  709 

PROPORTIONS   OF   TKKTH    OF    WHEELS. 

Tooth*  —  Iii  computing  the  dimensions  of  a  tooth,  it  is  to  be 
considered  as  a  beam  lixed  at  one  end,  the  weight  suspended 
from  the  other,  or  face  of  the  beam  ;  and  it  is  essential  to  con- 
sider the  element  of  velocity,  as  its  stress  in  operation,  at  high 
velocity  with  irregular  action,  is  increased  thereby.  The  dimen- 
sions of  a  tooth  should  be  much  greater  than  is  necessary  to  resist 
the  direct  stress  upon  it,  as  but  one  tooth  is  proportioned  to  bear 
the  whole  stress  upon  the  wheel,  although  two  or  more  are 
actually  in  contact  at  all  times ;  but  this  requirement  is  in 
consequence  of  the  great  wear  to  which  a  tooth  is  subjected? 
the  shocks  it  is  liable  to  from  lost  motion  when  so  worn  as  to 
reduce  its  depth  and  uniformity  of  bearing,  and  the  risk  of  the 
breaking  of  a  tooth  from  a  defect.  A  tooth  running  at  a  low 
velocity  may  be  materially  reduced  in  its  dimensions  compared 
with  one  running  at  high  velocity  and  with  a  like  stress.  The 
result  of  operations  with  toothed  wheels,  for  a  long  period  of 
time,  has  determined  that  a  tooth  with  a  pitch  of  3  inches  and  a 
breadth  7.5  inches  will  transmit,  at  a  velocity  of  6.66  feet  per 
second,  the  power  of  59.16  horses. 

TO    COMPUTE    THE    DEPTH    OF    A    CAST-IKON    TOOTH. 

1.  When  the  stress  is  given. 

Rule* —  Extract  the  square  root  of  the  stress,  and  multiply  it 
by  .02. 

Exaiwple. — The  stress  to  be  borne  by  a  tooth  is  4886  Ibs.  ; 
what  should  be  its  depth? 

1/1886  x  .02  =  1.4  in. 

2.  When  the  horse-power  is  given. 

Rule. — Extract  the  square-root  of  the  quotient  of  the  horse- 
power divided  by  the  velocity  in  feet  per  second,  and  multiply  it 
by  ,466, 


710  HANDBOOK    ON    ENGINEERING. 

Example.  —  The  horse-power  to  be  transmitted  by  a  tooth  is 
60,  and  the  velocity  of  it  at  its  pitch-line  is  6.66  feet  per  second ; 
what  should  be  the  depth  of  the  tooth  ? 

60  x  .466  =  1.898  in. 


6.66 


TO    COMPUTE  THE   HORSE -POWER  OF  A  TOOTH. 

Rule*  —  Multiply  the  pressure  at  the  pitch-line  by  its  velocity 
in  feet  per  minute,  and  divide  the  product  by  33,000. 

CALCULATING  SPEED  WHEN  TIME  IS  NOT  TAKEN  INTO  ACCOUNT. 

Rule*  —  Divide  the  greater  diameter,  or  number  of  teeth, 
by  the  lesser  diameter  or  number  of  teeth,  and  the  quotient  is 
the  number  of  revolutions  the  lesser  will  make,  for  one  of  the 
greater. 

Example.  — How  many  revolutions  will  a  pinion  of  20  teeth 
make,  for  1  of  a  wheel  with  125? 

125  divided  by  20  =  6.25  or  6J  revolutions. 

To  find  the  number  of  revolutions  of  the  last  to  one  of  the  first, 
in  a  train  of  wheels  and  pinions  :  — 

Rule*  —  Divide  the  product  of  all  the  teeth  in  the  driving  by 
the  product  of  all  the  teeth  in  the  driven  ;  and  the  quotient  equals 
the  ratio  of  velocity  required. 

Example  1. — Required  the  ratio  of  velocity  of  the  last,  to  1 
of  the  first,  in  the  following  train  of  wheels  and  pinions,  viz. : 
pinions  driving  —  the  first  of  which  contains  10  teeth,  the  second 
15,  and  third  18.  Wheels  driven,  first  teeth  15,  second  25, 

10xl5x  18 
and   third   32.      ^ — ^ — ^-0  =  .225  of    a  revolution   the    wheel 

1.0  X  20  X  O ij 

will  make  to  one  of  the  pinion. 

Example  2. — A  wheel  of  42  teeth  giving  motion  to  1  of  12, 
on  which  shaft  is  a  pulley  of  21  inches  diameter,  driving  1  of  6  ; 


HANDBOOK    ON    ENGINEERING.  711 

required  the  number  of  revolutions  of  the  last  pulley  to   1   of  the 

42x21 
first   wheel.     ^       „==  12.-25  or  12J  revolutions. 

NOTE.  —  Where  increase  or  decrease  of  velocity  is  required  to 
be  communicated  by  wheel- work,  it  has  been  demonstrated  that 
the  number  of  teeth  on  each  pinion  should  not  be  less  than  1  to 
6  of  its  wheel,  unless  there  be  some  other  important  reason  for  a 
higher  ratio. 

WHEN    TIME    MUST  BE    REGARDED. 

Rule*  —  Multiply  the  diameter  or  number  of  teeth  in  the  driver 
by  its  velocity  in  any  given  time,  and  divide  the  product  by  the 
required  velocity  of  the  driven ;  the  quotient  equals  the  number 
of  teeth  or  diameter  of  the  driven,  to  produce  the  velocity 
required. 

Example  1.  —  If  a  wheel  containing  84  teeth  makes  20  revolu- 
tions per  minute,   how  many  must  another  contain,  to  work  in 
contact,  and  make  60  revolutions  in  the  same  time: 
80x20  divided  by  60=27  teeth. 

Example  2.  —  From  a  shaft  making  45  revolutions  per  minute 
and  with  a  pinion  9  inches  diameter  at  the  pitch-line,  I  wish 
to  transmit  motion  at  15  revolutions  per  minute ;  what,  at  the 
pitch-line,  must  be  the  diameter  of  the  wheel? 

45  x  9  divided  by  15  =  27  inches. 

ExampleS.  —  Required  the  diameter  of  a  pulley  to  make  16 
revolutions  in  the  same  time  as  one  of  24  inches  making  36. 
24  x  36  divided  by  16  =  54  inches. 

The  distance  between  the  centers,  and  the  velocities  of  two  wheels 
being  given,  to  find  their  proper  diameters :  — 

Rale«.  —  Divide  the  greatest  velocity  by  the  least ;  the  quo- 
tient is  the  ratio  of  diameter  the  wheels  must  bear  to  each  other. 
Hence,  divide  the  distance  between  the  centers  by  the  ratio  -f  1 ; 
the  quotient  equals  the  radius  of  the  smaller  wheel ;  and  subtract 


712  HANDBOOK    ON    ENGINEERING. 

the  radius  thus  obtained  from  the  distance  between  the  centers; 
the  remainder  equals  the  radius  of  the  other. 

Example.  — The  distance  of  two  shafts  from  center  to  center 
is  50  in.  and  the  velocity  of  the  one  25  revolutions  per  minute, 
the  other  is  to  make  80  at  the  same  time ;  the  proper  diameters 
of  the  wheels  at  the  pitch  line  are  required. 

80  divided  by  25  =  3.2,  ratio  of  velocity,  and  50  divided  by 
3.2  +  1  =  11.9,  the  radius  of  the  smaller  wheel;  then  50  minus 
11.9  =y  38.1,  radius  of  larger  ;  their  diameters  are  11.9  x  2  =  23.8 
and  38.1x2  =  76.2  in. 

To  obtain  or  diminish  an  accumulated  velocity  by  means  of 
wheels  and  pinions,  or  wheels,  pinions  and  pulleys,  it  is  necessary 
that  a  proportional  ratio  of  velocity  should  exist,  and  which  is 
thus  attained  ;  multiply  the  given  and  required  velocities  together ; 
and  the  square  root  of  the  product  is  the  mean  or  proportionate 
velocity. 

Example. — Let  the  given  velocity  of  a  wheel  containing  54 
teeth  equal  16  revolutions  per  minute,  and  the  given  diameter  of 
an  intermediate  pulley  equal  25  in.,  to  obtain  a  velocity  of  81 
revolutions  in  a  machine ;  required  the  number  of  teeth  in  the 
intermediate  wheel  and  diameter  of  the  last  pulley. 

7  81x16  ==  36  mean  velocity  ;  54  x  16  divided  by  36  =  24 
teeth,  and  25x36  divided  by  81  =  11.1  in.,  diameter  of  pulley. 

TABLE    OF    THE    WEIGHT    OF      A      SQUARE     FOOT      OF      SHEET    IRON    IX 
POUNDS    AVOIRDUPOIS. 

No.  1  is  T5^  of  an  inch  ;  No.  4,  J ;  No.  11,  J,  etc. 

No.  on  wire  gauge,  1234     5     6     7     8     9      10     11     12 
Pounds  avoir.,       12.5  12    11     10    9     8   7.5    7     6    5.68    5    4.62 

No.  on  wire  gauge,    13   14    15    16    17      18       19 20 21. 22^ 

Pounds  avoir.,        4.31  4   3.95  3   2.5  2.18  1.93     1.62    1.5     1.37 


HANDBOOK    ON    ENGINEERING.  713 

SCREW-CUTTING. 

In  a  lathe  properly  adapted,  screws  to  any  degree  of  pitch,  or 
number  of  threads  in  a  given  length,  may  be  cut  by  means  of  a 
leading  screw  of  any  given  pitch,  accompanied  with  change  wheels 
and  pinions  ;  coarse  pitches  being  effected  generally  by  means  of 
one  wheel  and  one  pinion  with  a  carrier,  or  intermediate  wheel, 
which  cause  no  variation  or  change  of  motion  to  take  place  ;  hence, 
the  following :  — 

Rule*  —  Divide  the  number  of  threads  in  a  given  length  of  the 
screw  which  is  to  be  cut,  by  the  number  of  threads  in  the  same 
length  of  the  leading  screw  attached  to  the  lathe,  and  the  quotient 
is  the  ratio  that  the  wheel  on  the  end  of  the  screw  must  bear  to 
that  on  the  end  of  the  lathe  spindle. 

Example. — -Let  it  be  required  to  cut  a  screw  with  5  threads 
in  an  inch,  the  leading  screw  being  of  i  inch  pitch,  or  containing 
2  threads  in  an  inch  ;  what  must  be  the  ratio  of  wheels  applied? 

5  divided  by  2  =  2.5,  the  ratio  they  must  bear  to  each  other. 
Then  suppose  a  pinion  of  40  teeth  be  fixed  upon  for  the  spindle ; 
40  x  2.5  =  100  teeth  for  the  wheel  on  the  end  of  the  screw. 

But  screws  of  a  greater  degree  of  fineness  than  about  8  threads 
in  an  inch  are  more  conveniently  cut  by  an  additional  wheel  and 
pinion,  because  of  the  proper  degree  of  velocity  being  more 
effectively  attained,  and  these,  on  account  of  revolving  upon  a 
stud,  are  commonly  designated  the  stud- wheels,  or  stud-wheel 
and  pinion  ;  but  the  mode  of  calculation  and  ratio  of  screw  are  the 
same  as  in  the  preceding  rule.  Hence,  all  that  is  further  neces- 
sary is  to  fix  upon  an^  three  wheels  at  pleasure,  as  those  for  the 
spindle  and  stud-wheels  ;  then  multiply  the  number  of  teeth  in 
the  spindle-wheel  by  the  ratio  of  the  screw  and  by  the  number  of 
teeth  in  that  wheel  or  pinion  which  is  in  contact  with  the  wheel 
on  the  end  of  the  screw  ;  divide  the  product  by  the  stud-wheel  in 
contact  with  the  spindle- wheel,  and  the  quotient  is  the  number  of 
teeth  required  in  the  wheel  on  the  end  of  the  leading  screw. 


714 


HANDBOOK    ON    ENGINEERING. 


Example.  —  Suppose  a  screw  is  required  to  be  cut  containing 
25  threads  in  an  inch,  and  the  leading  screw,  as  before,  having 
two  threads  in  an  inch,  and  that  a  wheel  of  60  teeth  is  fixed  upon 
for  the  end  of  the  spindle,  20  for  the  pinion  in  contact  with  the 
screw-wheel,  and  100  for  that  in  contact  with  the  wheel  on  the 
end  of  the  spindle ;  required  the  number  of  teeth  in  the  wheel  for 
the  end  of  the  leading  screw. 

,  60x  12.5x20 
25  divided  by  2  =  12.5,  and  _    -j^—       =  150  teeth. 

Or  suppose  the  spindle  and  screw  wheels  to  be  those  fixed  upon, 
also  any  one  of  the  stud- wheels,  to  find  the  number  of  teeth  in  the 
other. 

150x100  60  x  12. 5  x  20 

=  20  teeth,  or — =  100  teeth. 


60x12.5 


150 


Transmission  of  Power  by  Manilla  Rope, 
power  Transmitted. 


Horse- 


Feet  per  minute  .... 

1000 

1500 

2000 

2500 

3000 

3500 

4000 

4500 

5000 

Diameter  of  Rope  .  f 
((  a  i 

«  "  .'  14 

"  "  •  14 
"  "  .  l| 

u  "  .  2 

U 
34 
6* 
74 
10 
13 

2| 
*S 
74 
11 
15 
194 

a 

104 

15 

20 
26 

44 
8 
13 
18 
25 
33 

54 
10 
15 
22 
30 
39 

64 
11 
18 
26 
35 
46 

7 
13 
20 
30 
40 
52 

8 
15 
23 
34 
45 
59 

9 
16 
26 
37 
50 
65 

Decimal  Equivalents  of  One  Foot  by  Inches. 


4 

4 

1 

1 

2 

*     '  '* 

5 

.0208 

.0417 

.0626 

.0833 

.1667 

.2500 

.3333 

.4167 

6 

7 

8 

9 

10 

11 

12 

.5000 

.5833 

.6667 

.7510 

.8333 

.9167 

1.000 

HANDBOOK    ON    ENGINEERING. 


715 


TABLE  OF  TRANSMISSION  OF  POWER  BY 
WIRE  ROPES. 

This  table  is  based  upon  scientific  calculations,  careful  observations 
and  experience,  and  can  be  relied  upon  when  the  distance  exceeds  100 
feet.  We  also  find  by  experience  that  it  is  best  to  run  the  Wire  Rope 
Transmission  at  the  medium  number  of  revolutions  indicated  in  the  table, 
as  it  makes  the  best  and  smoothest  running  transmission.  If  more 
power  is  needed  than  is  indicated  at  80  to  100  revolutions,  choose  a 
larger  diameter  of  sheave. 


Diameter  of 
Sheave  in  ft. 

Number  of 
Revolutions. 

Diameter  of 
Rope. 

' 

Horse- 
Power. 

Diameter  of 
Sheave  in  ft. 

Number  of 
Revolutions. 

Diameter  of 
Rope. 

Horse  - 
Power. 

3 

80 

1 

3 

7 

140 

A 

35 

3 

100 

8 

3i 

8 

80 

26 

3 

120 

1 

4 

8 

100 

i 

32 

3 

140 

*i 

8 

120 

1 

39 

4 

80 

1 

4 

8 

140 

1 

45 

4 

100 

i 

5 

9 

80 

{At 

\   47 

i   48 

4 

120 

1 

6 

9 

100 

{At 

1   58 

/   60 

4 

140 

i 

7 

9 

120 

{A  i 

1    69 
/    73 

5 

30 

ft 

9 

9 

140 

fM 

1    82 

I   84 

5 

100 

A 

11 

10 

80 

{l  tt 

1   64 

/    68 

5 

120 

-h 

13 

10 

100 

(I  ft 

\   80 

/    85 

5 

140 

& 

15 

10 

120 

{!  H 

\   96 
J  102 

6 

80 

h 

14 

10 

140 

{Hi 

\112 
(119 

6 

100 

h 

17 

12 

80 

{ftj 

\   93 
jf   99 

6 

120 

h 

20 

12 

100 

{HI 

\116 
/  124 

6 

140 

h 

23 

12 

120 

(in 

\140 
J  149 

7 

80 

A 

20 

12 

120 

i 

173 

7 

100 

A 

26 

14 

80 

{.H 

1141 

/148 

-7 

120 

A 

30 

14 

100 

{'« 

\176 
/185 

716  HANDBOOK    ON    ENGINEERING. 


CHAPTER    XXV. 
ELECTRIC  ELEVATORS. 

In  factories,  warehouses  and  business  buildings,  freight,  and  in 
some  instances  passenger  elevators,  are  operated  by  machines 
that  are  arranged  to  be  driven  by  a  belt.  Such  machines  are 
variously  called  belted  elevators,  factory  elevators  and  sometimes 
warehouse  elevators. 

In  factories  where  there  is  a  line  of  shafting  kept  running 
continuously,  they  are  driven  from  it.  As  a  rule  the  elevator 
machine  is  driven  from  a  countershaft  which  latter  is  belted  to 
the  line  shaft.  Very  often  the  elevator  machine  is  driven 
directly  from  the  line  shaft.  As  the  line  shaft  runs  always  in  the 
same  direction,  the  only  way  in  which  the  elevator  machine  can 
be  made  to  run  in  both  directions  is  by  the  use  of  two  belts,  one 
open  and  the  other  crossed,  or  some  form  of  gearing  that  will 
accomplish  the  same  result.  The  common  practice  is  to  use 
double  belts.  Either  one  of  these  belts  can  be  made  to  drive  by 
using  friction  clutches,  or  by  having  tight  and  loose  pulleys,  and 
a  belt  shifter.  The  latter  arrangement  is  the  most  common. 

In  buildings  where  there  is  no  line  of  shafting,  power  for  oper- 
ating the  elevator  machine  must  be  derived  from  some  kind  of 
motor  installed  expressly  for  the  purpose.  Nowadays  electric 
motors  are  very  extensively  used  for  this  purpose,  and  the  com- 
bination of  an  elevator  machine  and  an  electric  motor  to  drive  it  is 
very  generally  called  an  electric  elevator,  although  in  reality  it  is  not 
such,  but  simply  a  belted  elevator  machine  driven  by  an  electric 
motor.  It  has  become  so  common,  however,  to  call  such  com- 
binations electric  elevators,  that  true  electric  elevators  are  generally 
designated  as  "  direct  connected  electric  elevators." 


HANDBOOK    ON    ENGINEERING.  717 

The  first  impression  would  be  that  in  the  combination  of  a 
belted  elevator  machine,  and  an  electric  motor  to  drive  it,  as  the 
motor  simply  furnishes  the  power  to  set  the  machine  in  motion, 
there  can  be  nothing  about  the  combination  that  requires  any 
special  elucidation.  Such  a  conclusion,  however,  would  not  be 
correct,  for  there  are  several  ways  in  which  the  combination  can 
be  arranged,  and  in  what  follows  I  propose  to  explain  these 
several  combinations,  pointing  out  the  important  features  of 
each. 

The  simplest  way  in  which  a  motor  can  be  installed  to  drive 
an  elevator,  is  to  arrange  it  so  as  to  drive  the  counter  shaft  con- 
tinuously, in  which  case  the  elevator  is  stopped  and  started  by 
throwing  the  belts  on  the  tight  or  the  loose  pulley.  Although 
this  is  a  very  simple  arrangement,  it  is  not  desirable  unless  the 
elevator  is  kept  in  service  all  the  time.  In  buildings  where  the 
elevator  is  used  only  at  intervals,  a  great  amount  of  power  is 
wasted  if  the  shafting  is  kept  running  all  the  time  ;  hence  it  is 
desirable  to  arrange  the  motor  so  that  it  can  be  stopped  when  the 
elevator  is  stopped,  and  started  whenever  the  elevator  is  to  be 
used. 

If  the  motor  is  arranged  so  as  to  run  all  the  time,  it  is  provided 
with  a  simple  motor-starting  switch,  the  same  as  is  used  for  any 
motor  installed  to  operate  machinery  of  any  kind.  If  the  motor 
is  started  and  stopped  whenever  the  elevator  is  started  and  stopped, 
it  is  necessary  to  provide  a  motor-starter  that  can  be  operated 
from  the  elevator  car.  A  very  common  way  of  arranging  a  motor 
to  start  and  stop  with  the  elevator  is  illustrated  in  the  diagram 


In  this  diagram  the  elevator  car  is  shown  at  (7,  with  the  lifting 
ropes  running  over  the  sheave  F  at  the  top  of  the  elevator 
shaft,  and  then  down  and  around  the  drum  A  of  the  elevator 
machine.  This  drum  is  driven  by  means  of  screw  gearing,  as  a 
rule,  with  driving  pulieys  on  the  screw  shaft  as  shown  at  B  The 


718 


HANDBOOK    ON    ENGINEERING. 


driving  motor  is  shown  at  Jf,  and  the  counter-shaft  to  which  it  is 
belted  is  at  D.  In  this  arrangement  the  elevator  machine  is  pro- 
vided with  a  tight  center  pulley  and  loose  pulleys  on  the  two  sides. 
The  belts  are  shown  on  the  loose  pulleys,  one  being  open  and  the 


other  being  crossed .  The  countershaft  carries  a  drum  wide 
enough  to  allow  for  the  side  movement  of  the  belts  when  one  or 
the  other  is  shifted  upon  the  tight  center  pulley  by  the  belt  shifter 
s.  To  operate  the  elevator  car,  a  hand  rope  is  provided  which 


HANDBOOK    ON    ENGINEERING.  719 

runs  up  the  elevator  shaft  at  one  side  of  the  car  from  bottom  to 
top  of  building.  This  rope  is  shown  in  the  diagram  at  Z,  and 
runs  around  two  small  sheaves  a  a.  The  lower  one  of  these  sheaves 
is  provided  with  a  crank  pin  which  moves  the  connecting  rod  6, 
and  thus  rocks  the  lever  r,  and  thereby  moves  the  belt  shifter  s. 
To  cause  the  car  to  ascend  the  hand  rope  I  is  pulled  down,  and 
to  make  the  car  descend,  the  hand  rope  is  pulled  up.  As  will  be 
seen  from  this  explanation,  the  lower  sheave  a  will  rotate  in  one 
direction  when  the  hand  rope  is  pulled  to  make  the  car  go  up,  and 
in  the  opposite  direction  when  the  rope  is  pulled  to  make  the  car 
run  down.  In  the  diagram,  sheave  a  is  shown  in  the  stop  posi- 
tion, therefore  when  the  hand  rope  is  pulled  down  so  as  to  make 
the  car  run  up,  the  sheave  will  turn  in  a  direction  opposite  to  the 
movement  of  the  hands  of  a  clock,  and  thus  the  belt  shifter  will 
be  moved  to  the  right,  and  the  open  belt  will  be  run  onto  the  tight 
center  pulley.  If  the  hand  rope  is  pulled  up  sheave  a  will  rotate 
in  the  direction  of  the  hands  of  a  clock,  and  the  belt  shifter  will 
move  toward  the  left  and  thus  shift  the  crossed  belt  onto  the  tight 
pulley.  The  rope  p  is  a  stop  rope  and  is  connected  with  the  two 
sides  of  the  hand  rope  in  the  manner  shown,  so  that  when  the  car 
is  running  in  either  direction,  if  p  is  pulled  hard  it  will  bring  I  to 
the  position  shown  in  the  diagram,  and  thus  stop  the  car.  This 
rope  can  be  dispensed  with,  but  the  objection  is  that  in  pulling 
the  hand  rope  I  to  stop  the  car  it  may  be  pulled  too  far  and  then 
the  car  will  not  only  be  stopped  but  it  will  be  caused  to  run  in 
the  opposite  direction. 

The  motor  starting  switch  is  shown  at  E,  the  line  wires  being 
connected  with  the  two  top  binding  posts.  The  lever  c  c  is  in  one 
piece  and  is  independent  of  lever  e,  but  both  swing  around  the 
same  pivot.  At  w,  a  dash  pot  is  provided  which  acts  to  prevent 
the  too  rapid  movement  of  lever  e.  As  will  be  noticed,  lever  c 
has  a  projection  which  holds  lever  e  up.  The  operation  of  this 
motor  starter  is  as  follows :  When  the  hand  rope  I  is  pulled  in 


720  HANDBOOK    ON    ENGINEERING. 

either  direction,  the  rope  h  draws  lever  c  towards  the  left  and 
causes  it  to  make  contact  with  the  switch  jaw  j.  In  this  way  the 
current  from  the  upper  binding  post  which  is  connected  with  j 
through  wire  #,  passes  to  lever  e,  and  thus  to  the  starting  resist- 
ance, which  is  indicated  by  the  dotted  lines  t,  to  binding  post  &, 
from  where  it  goes  to  the  motor  armature  through  wire  c?,  and  re- 
turns through  the  other  wire  d  to  the  upper  binding  post  at  the 
right  side,  which  is  connected  with  the  opposite  side  of  the  main 
line,  thus  completing  the  circuit.  The  field  current  branches  off 
from  the  upper  end  of  the  starting  resistance  t  and  reaches  the 
field  coils  through  wire /,  and  through  the  lower  wire  /  reaches 
the  return  armature  wire  d  and  thus  the  opposite  side  of  the  cir- 
cuit. When  the  rope  h  pulls  lever  c  over  toward  the  left,  the  lever 
e  does  not  follow  it,  as  it  is  held  up  by  the  dash  pot  m.  The 
weight  on  the  end  of  .e  gradually  overcomes  the  resistance  of  the 
dash  pot,  and  thus  causes  lever  e  to  move  downward  slowly.  The 
velocity  at  which  e  moves  downward  is  graduated  by  adjusting 
the  opening  in  the  dash  pot  through  which  the  oil  flows. 

From  the  foregoing  it  will  be  seen  that  the  starter  E  is  made  so 
as  to  accomplish  automatically  just  what  a  man  accomplishes 
when  he  moves  the  lever  of  an  ordinary  motor-starter  ;  that  is,  it 
first  closes  the  circuit  through  the  motor,  by  bringing  lever  c  into 
contact  withj;  and  then  allows  lever  e  to  move  slowly  so  as 
to  cut  the  resistance  i  out  of  the  armature  circuit  gradually. 
When  the  elevator  is  stopped,  by  pulling  the  hand  rope  /  to  the 
stop  position,  the  rope  h  slacks  up  and  then  the  weight  on  the  end 
of  lever  c  causes  it  to  descend,  and  thus  return  lever  e  to  the  posi- 
tion shown  in  the  diagram,  and  also  to  break  the  circuit  between 
c  and  j. 

The  elevator  machine  A  is  provided  with  a  brake  which  is 
actuated  by  the  belt  shifter  s,  so  that  when  the  belts  are  shifted 
upon  the  side  pulleys,  as  shown  in  the  diagram,  the  brake  is  put 
on,  and  thus  the  machine  is  stopped.  As  soon  as  the  belt  shifter 


HANDBOOK    ON    ENGINEERING.  721 

moved  to  set  the  car  in  motion  the  brake  is  raised,  so  as  to 
allow  the  machine  to  run  free. 

This  arrangement  is  used  very  extensively,  although  the  motor- 
sttrtiug  switch  is  not  always  made  in  strict  accordance  with  the 
on^  shown  at  E.  In  fact,  there  are  a  great  many  different  designs 
on  the  market,  but  they  all  accomplish  the  same  result,  although 
the  means  employed  may  be  very  different. 

Although  it  is  very  advantageous  to  have  the  motor  arranged 
as  in  Fig.  1,  so  that  it  may  be  stopped  and  started  together  with 
the  elevator,  there  is  one  objection  to  it  which  is  sometimes  re- 
garded as  serious,  and  that  is,  that  as  it  requires  a  great  amount 
of  power  to  start  an  elevator  from  a  state  of  rest,  the  motor  will 
take  a  very  strong  current  in  the  act  of  starting.  To  get  around 
this  objection,  it  is  a  common  practice  to  provide  a  separate  rope 
for  starting  the  motor,  and  then  when  it  is  desired  to  use  the  ele- 
vator, the  motor  rope  is  pulled  first,  and  in  half  a  minute  or  so, 
the  main  hand  rope  is  pulled.  In  this  way  the  motor  gets  a  start 
ahead  of  the  elevator,  and  the  headway  of  the  motor  armature 
helps  to  set  the  elevator  car  in  motion,  so  that  the  current  taken 
by  the  motor  to  start  the  elevator  is  very  much  reduced. 

When  a  separate  rope  is  used  to  start  the  motor  in  advance  of 
the  elevator,  the  starter  E,  or  the  levers  connecting  with  it,  are 
made  so  that  while  the  motor  can  be  started  independently  of  the 
elevator  car,  when  the  main  hand  rope  is  pulled  to  stop  the  car, 
it  also  stops  the  motor.  If  this  arrangement  were  not  provided, 
the  operator  might  stop  the  elevator  and  forget  to  stop  the  motor, 
in  which  case  the  latter  would  keep  on  running  and  waste  power. 

The  main  hand  rope  I  is  provided  with  stops  at  top  and 
bottom  of  the  elevator  shaft,  so  that  the  car  may  be  stopped  auto- 
matically should  the  operator  forget  to  pull  the  hand  rope  at  the 
proper  time. 

It  is  the  universal  practice  with  elevator  machines  of  the  type 
shown  in  Fig.  1  to  counterbalance  the  elevator  car,  but  I  have 
not  shown  a  counterbalance  in  this  diagram  as  it  would  only  serve 

46 


722 


HANDBOOK    ON    ENGINEERING. 


to  complicate  its  appearance,  and  it  is  not  necessary  to  show  it  ae 
the  electrical  features  .will  be  the  same  whether  there  is  a  counter- 
balance or  not.  This  diagram  also  shows  a  separate  rope  h  fcr 
actuating  the  starter  E,  but  in  actual  machines  E  is  generaly 


CONTROLLER 


CLCYATQR 

DIAGRAM  -SHOWING  CONNECTIONS 
GRAVITY    MOTOR  CONTROLLER 
ELEVATOf? 


MOTOR 


operated  from  the  lower  sheave  a,  which  also  actuates  the  belt- 
shifter. 

Fig*  2   is   a  diagram  that  shows  the  way  in  which  one  of  the 
various  motor  starters  in  actual  use  is  connected  with  the  motor 


HANDBOOK    ON    ENGINEERING. 


723 


and  the  operating  hand  rope.  In  this  illustration  A  is  the  lower 
sheave  a  of  Fig.  1,  and  F  represents  the  hoisting  drum  and  E  the 
diiving  pulleys  of  the  elevator  machine,  G  being  the  lifting  ropes 
from  which  the  car  is  suspended.  The  sheave  A  is  rotated 


DIAGRAM  OF  CONNECTIONS  OF  A 

GRAVITY  MOTOR  CONTROLLER. 
W/TH  SEPCRATE  ROPE  ATTA CHMCNT. 


CT'ia  -O 


MOTOR. 


through  one  quarter  of  a  turn  in  either  direction  by  the  pull  on 
the  hand  rope  B,  and  when  so  rotated  shifts  the  belt  shifter  and 
also  lifts  the  brake  from  the  brake-wheel.  At  the  same  time  the 
crank  pin  C  pulls  up  the  connecting  rod,  and  thus  the  upper  end 


724  HANDBOOK    ON    ENGINEERING. 

of  rod  c,  which  takes  the  place  of  lever  c  in  Fig.  1.  In  this 
way  the  switch  blades  in  the  lower  end  of  c  are  raised  into  con- 
tact with  the  clips  jj,  which  take  the  place  of  contact,;  in  Fig.  1, 
and  thus  the  circuit  is  closed.  A  projection  s  on  c  holds  ohe 
switch  e  in  the  upper  position,  but  when  c  is  raised,  s  goes  up  with 
it,  and  then  e  is  free  to  descend  by  the  force  of  gravity  accing 
upon  the  weight  w.  The  dash  pot  m  is  set  so  as  to  retard  the 
movement  of  e  as  much  as  may  be  desired.  The  outer  end  of  e 
glides  over  the  contacts  i  in  its  downward  movement,  and  thus 
cuts  out  of  the  armature  circuit  the  starting  resistance.  This 
resistance  is  contained  in  the  controller  box. 

Fig*.  3  shows  the  same  type  of  controller  as  in  Fig.  2,  but  it  is 
arranged  so  that  the  motor  may  be  started  ahead  of  the  elevator. 
The  separate  motor-starting  rope  is  shown  at-//".  When  this  rope 
is  pulled,  it  elongates  the  spiral  spring  A"  which  is  connected  with 
the  stud  G  fixed  in  the  upper  end  of  rod  c.  The  rope  //  is  pulled 
up  enough  to  stretch  K  until  the  lever  Dis  lifted,  H  being  attached 
to  its  outer  end  L  When  D  is  lifted  sufficiently,  its  inner  end  dis- 
engages the  stud  G,  and  allows  it  to  slide  upward  in  the  slot 
shown  in  dotted  lines,  in  the  lower  end  of  the  connecting  rod. 
In  this  way  the  motor  is  started  ahead  of  the  elevator  machine. 
If  now  the  elevator  machine  is  started,  by  pulling  on  the  main 
hand  rope  FF^  the  crank  pin  C"  on  the  hand  rope  sheave  will  lift 
the  connecting  rod  (7,  and  when  it  reaches  its  upper  position,  the 
catch-lever  D  will  drop  into  the  position  shown  in  the  illustration, 
and  thus  lock  the  stud  6r,  so  that  when  the  elevator  is  stopped, 
the  rotation  of  the  hand  rope  sheave  will  push  rod  C  downward 
and  thus  stop  the  motor,  as  well  as  shift  the  belts  and  stop  the 
elevator  machine. 

In  the  three  illustrations  shown  the  motor  is  run  always  in  the 
same  direction  and  the  reversing  of  the  direction  of  rotation  of 
the  hoisting  drum  is  effected  by  the  use  of  double  belts  and  a 
belt  shifter,  or  friction  clutches  which  cause  one  or  the  other  of 


HANDBOOK    ON    ENGINEERING.  725 

the  belts  to  do  the  driving.     The  way  in  which  machines  of   this 


type  are  installed  can  be  more  fully  understood  from  Fig.  4, 


726  HANDBOOK    ON    ENGINEERING. 

This  figure  shows  the  position  of  the  motor,  the  countershaft 
and  the  elevator  machine  with  reference  to  the  elevator  shaft. 
This  illustration  is  so  clear  that  an  explanation  of  it  would  be 
superfluous. 

In  relation  to  the  installation  of  elevator  plants  of  this  type 
all  that  need  be  said  is  that  the  motor  must  be  of  the  shunt 
type,  the  same  as  those  used  for  driving  machines  of  any  kind. 
A  series  wound  motor,  such  as  are  used  for  electric  railway 
cars,  must  not  be  used.  Shunt  wound  motors  cannot  run  above  a 
certain  speed,  unless  forced  to  do  so  by  power  applied  from  an 
external  source,  and  in  such  an  event  they  become  generators  of 
electricity  and  thus  resist  rotation.  On  this  account,  when  they 
are  used  for  elevator  service,  they  not  only  move  the  elevator  car, 
but  when  the  latter  is  descending  under  the  influence  of  a  heavy  load 
and  tends  to  run  away,  the  motor  at  once  begins  to  act  as  a  gen- 
erator, and  is  thus  converted  into  a  brake  which  holds  the  car  and 
prevents  it  from  attaining  a  speed  much  above  the  normal ;  in 
fact,  the  difference  between  the  car  velocity  when  lifting  a  heavy 
load,  and  when  running  down  under  the  influence  of  a  similar  load 
is  hardly  enough  to  be  noticed  by  any  one  not  familiar  with  the 
elevator. 

The  motor  in  these  combinations  is  to  be  given  the  same  care 
as  those  used  for  other  purposes ;  that  is,  it  must  be  kept  clean 
and  the  brushes  properly  set  so  as  to  run  with  as  little  spark  as 
is  possible.  The  controller  switch  requires  more  attention  than  the 
motor  starters  used  with  stationary  motors,  for  the  simple  reason 
that  it  is  used  to  a  much  greater  extent.  Every  time  the  elevator 
is  started  or  stopped  the  controller  switch  is  actuated,  hence,  the 
switch  levers  are  subjected  to  a  considerable  amount  of  wear,  and 
the  contacts  are  liable  to  become  rough,  either  by  cutting  or  by 
being  burned  on  account  of  making  imperfect  contact.  On  this 
account  the  contact  must  be  well  examined  at  least  once  every 
day,  and  if  burned  or  rough  must  be  smoothed  up.  It  is  also 


HANDBOOK    ON    ENGINEERING. 


727 


necessary  to  see  that  all  parts  of  the  controller  are  properly  se- 
cured, that  none  of  the  screws  or  pins  are  working  out,  and  that 
the  contacts  and  switch  levers  are  not  out  of  their  normal  posi- 
tion. 


As  electric  motors  can  be  run  as  well  in  one  direction  as  the 
other,  and  as  all  that  is  required  to  make  any  motor  reversible  is 
to  provide  a  reversing  switch,  it  can  be  seen  at  once  that  by  mak- 
ing use  of  such  a  switch,  the  direction  of  movement  of  the  ele- 


728  HANDBOOK    ON    ENGINEERING. 

vator  car  can  be  reversed  by  simply  reversing  the  motor,  and  thus 
do  away  with  the  complication  of  a  countershaft  and  tight  and 
loose  pulleys.  Owing  to  this  fact  elevator  machines  are  now 
made  so  as  to  be  used  with  reversing  motors.  These  are  usually 
called  single-belt  machines.  The  way  in  which  such  machines 
are  connected  with  the  motor  and  the  type  of  controller  required 
can  be  understoood  from  the  diagram  Fig.  5. 

As  will  be  seen,  the  principal  difference  in  the  machine  itself 
is  that  the  tight  and  loose  pulleys  are  replaced  by  a  single  tight 
pulley  which  is  only  wide  enough  to  carry  the  driving  belt. 
Usually  an  extra  pulley  is  provided  for  the  brake,  and  this  brake 
is  mechanically  operated  in  the  same  manner  as  upon  machines 
provided  with  shifting  belts.  Another  modification  which  is 
sometimes  used,  but  is  not  shown  in  the  diagram,  is  the  arrange- 
ment of  a  brake  so  that  same  is  operated  by  a  magnet 
instead  of  by  mechanical  means.  With  this  arrangement  the 
magnet  is  arranged  so  that  when  the  machine  is  in  motion,  the 
current  passing  through  the  magnet  coil  acts  to  lift  the  brake, 
and  when  the  machine  stops,  the  magnet  lets  go,  and  the  brake 
goes  on.  By  arranging  the  brake  in  this  way  it  becomes  perfectly 
safe ;  for  if  the  brake  magnet  fails  to  act,  the  brake  will  not  be 
raised,  and  the  .machine  will  not  move ;  that  is,  failure  of  the 
device  to  work  properly  will  not  permit  the  elevator  car  to  move, 
thus  call  ing  attention  to  the  fact  that  something  is  out  of  order. 

The  operation  of  the  reversing  controller  is  as  follows :  the 
current  from  the  line  wires  passes  along  the  dotted  connections 
h  h  to  the  contact  ?',£,  i,i.  The  upper  left  hand  i  contact  is  con- 
nected with  the  lower  right  hand  one,  and  the  upper  right  hand 
with  the  lower  left  hand.  The  switch  lever  c  is  connected  with 
lever  e  by  means  of  the  two  springs  r  r,  so  that  c  may  be  moved 
either  up  or  down  without  carrying  e  with  it.  The  curved  con- 
tact o  is  connected  with  j  and  the  stud  around  which  c  and  e 
swing  is  connected  with  &,  while  g  is  connected  with  the  ends  of 


HANDBOOK  ON    ENGINEERING.  729 

the  starting  resistance  n  n  by  means  of  the  wire /and  the  two 
wires  s  s.  If  the  hand  rope  I  is  pulled  so  as  to  carry  lever  c 
upward,  the  current  from  the  left  side  line  wire  will  pass  through 
upper  left  side  i  contact,  to  o,  and  thence  to  j  and  through  wire  b 
to  the  motor  armature  and  returning  through  the  other  b  wire  will 
reach  g  and  then'pass  through  /  and  lower  s  to  lower  end  of  n  and 
thence  to  lever  e  and  the  inner  end  of  lever  c,  which  will  be  rest- 
ing on  the  upper  right  side  i  contact,  thus  reaching  the  right  side 
line  wire.  The  current  for  the  field  magnet  coils  will  be  drawn 
from  j  through  wire  d  and  back  to  k  through  the  other  wire  d. 
As  lever  c  has  been  moved  upward,  the  upper  spring  r  will  be 
compressed,  and  the  lower  one  will  be  stretched,  hence  a  force 
will  be  exerted  to  move  e  downward  over  the  lower  contacts  n  and 
thus  cut  out  the  starting  resistance,  As  in  the  case  of  the  con- 
troller in  Fig.  1  the  dash  pot  m  by  its  resistance  retards  the  move- 
ments of  e,  so  as  to  cut  out  the  resistance  as  gradually  as  may  be 
desired. 

In  the  chapter  on  stationary  motors  it  is  shown  that  to  prevent 
destructive  sparking,  when  the  starting  switch  is  opened,  the 
armature  and  field  coils  are  connected  so  as  to  form  a  permanently 
closed  loop.  This  style  of  connection  is  used  in  the  non-revers- 
ing controller  of  Fig.  1,  but  it  cannot  be  employed  with  a  revers- 
ing controller,  because  both  ends  of  the  armature  circuit  must  be 
free,  so  that  they  may  be  reversed  when  the  direction  of  rotation 
is  reversed.  As  this  connection  cannot  be  made,  a  very  common 
expedient  resorted  to  to  prevent  serious  sparking  when  the  switch 
is  opened  is  to  connect  a  string  of  incandescent  lamps  across  the 
terminals  of  the  field  circuit,  as  is  indicated  at  v  v  v.  These 
lamps,  together  with  the  field  coils,  form  a  closed  circuit,  so  that 
when  the  switch  is  opened,  the  field  can  discharge  through  the 
lamps,  and  thus  avoid  sparking  at  the  controller  contacts.  The 
only  objection  to  this  arangement  is  that  all  the  current  that 
passes  through  the  lamps  is  wasted,  but  by  placing  two  or  three 


730  HANDBOOK    ON    ENGINEERING. 

in  series  the  loss  is  reduced  to  an  insignificant  amount.  Another 
way  in  which  the  sparking  is  subdued,  but  only  to  a  slight  ex- 
tent, is  by  connecting  the  brake  magnet  coil  with  the  binding 
posts  j  and  fc,  which  is  the  simplest  and  most  generally  used  con- 
nection. The  brake  magnet  coil  together  with  the  field  coils  form 
a  closed  loop  when  connected  with  J  and  fc,  but  when  the  main  cir- 
cuit is  opened,  the  currents  flowing  in  the  two  coils  meet  each  other 
at  J  and  k  flowing  in  opposite  directions,  hence  they  both  follow 
along  the  main  circuit  and  try  to  jump  across  the  gaps  at  the 
switch,  and  thus  produce  about  as  much  sparking  as  if  they  were 
connected  independently  of  each  other.  In  tracing  out  the  path 
of  the  current  when  lever  c  is  moved  upward,  it  was  shown  that  the 
left  side  line  went  directly  to  the  upper  commutator  brush.  Now 
when  c  is  moved  downward,  this  same  line  wire  runs  to  the  lower 
commutator  brush  since  the  connections  between  the  two  upper 
i  contacts  and  the  two  lower  ones  are  crossed.  To  reverse  the 
direction  of  rotation  of  a  motor  all  that  is  required  is  to  reverse 
the  direction  of  the  current  through  the  armature,  that  through 
the  field  remaining  unchanged,  hence  it  will  be  seen  that  by  cross- 
ing the  connections  between  the  upper  and  lower  i  contacts,  the 
direction  of  rotation  of  the  motor  is  reversed  when  the  c  lever  is 
moved  in  opposite  directions. 

DIRECT  CONNECTED  ELECTRIC  ELEVATORS. 

The  machines  explained  in  the  foregoing  pages  are  simply 
combinations  of  an  electric  motor  and  a  belt  driven  electric  ma- 
chine, but,  as  already  stated,  they  are  commonly  spoken  of  as 
44  electric  elevators."  In  what  follows  it  is  proposed  to  explain 
the  construction  and  operation  of  true  electric  elevators,  which 
are  called  ' '  direct  connected  machines  ' '  to  distinguish  them  from 
the  combinations  so  far  described. 

There  are  many  designs  of  direct  connected  electric  elevators 


HANDBOOK    ON    ENGINEERING. 


731 


now  upon  the  market,  and  it  would  be  out  of  tbe  question  to  un- 
dertake to  describe  all  of  them  in  the  space  that  can  be  devoted 
to  the  subject  in  this  book.  On  that  account  the  discussion  will 
be  confined  to  the  designs  that  are  most  extensively  used.  The 
explanations  here  given,  however,  will  be  sufficient  to  enable  any 


Fig.  6. 

one  to  understand  the  operation  of  any  of  the  machines  not  de- 
scribed because  the  difference  in  the  principle  of  operation  is 
only  slight. 


732  HANDBOOK    ON    ENGINEERING. 

Perhaps  the  type  of  direct  connected  electric  elevator  that 
is  most  extensively  used  is  the  Otis  drum  elevator  with  hand 
rope  control  which  is  illustrated  in  Fig.  6.  This  machine  has 
been  upon  the  market  for  twelve  years  or  more,  and  is  stili  one  of 
the  standard  Otis  machines.  It  is  called  a  hand  rope  control 
machine  because  the  starting  and  stopping  is  controlled  by  the 
movement  of  a  hand  rope  that  passes  through  the  elevator  car. 
In  the  illustration,  the  sheave  around  which  the  hand  rope  passes 
can  be  seen  located  on  the  front  end  of  the  drum  shaft.  In  a 
modification  of  the  design,  this  sheave  is  mounted  upon  a  sep- 
erate  shaft  but  the  way  in  which  it  acts  is  the  same  as  in  the  pres- 
ent design.  When  the  hand  rope  is  pulled  the  sheave  is 
rotated  and  the  horizontal  bar,  running  from  it  to  the 
controller  box,  which  is  mounted  on  top  of  the  motor? 
shifts  the  starting  switch  so  as  to  run  the  machine  in 
the  direction  de'sired.  At  the  same  time,  the  vertical  lever  ex- 
tending upward  from  the  side  of  the  brake  wheel,  lifts  the  brake 
and  thus  frees  the  motor  shaft  so  that  it  may  revolve  unobstructed. 
The  motor  carries  a  worm  on  the  end  of  the  armature  shaft  which 
gears  into  the  under  side  of  a  worm  wheel  mounted  upon  the 
drum  shaft.  This  worm  wheel  runs  in  a  casing  seen  just  back  of 
the  hand  rope  sheave  wheel.  The  sheave  mounted  upon  the  shaft 
directly  above  the  drum  is  for  the  purpose  of  guiding  the  coun- 
terbalance ropes  which  run  up  from  the  back  of  the  drum.  In 
some  buildings  these  ropes  can  be  run  up  straight  from  the  back 
of  the  drum,  but  in  most  cases  they  must  run  up  in  the  elevator 
shaft  in  the  space  between  the  car  and  the  side  of  the  shaft.  As 
these  ropes  wind  upon  the  drum  from  one  side  to  the  other,  the 
guiding  sheave  mast  move  endwise  on  the  shaft,  hence  it  is  called 
a  traveling,  or  vibrating  sheave.  The  levers  seen  projecting  to 
the  right  of  the  machine  from  a  small  shaft  just  above  the  drum 
are  what  is  called  a  slack  cable  stop,  and  their  office  is  to  stop 
the  machine  if  the  lifting  cable  becomes  slack  through  the  w^ 


HANDBOOK    ON    ENGINEERING.  733 

ing  of  the  car  in  the  elevator  shaft  or  any  other  cause.  These 
levers  are  held  in  the  position  shown  when  the  lifting  ropes  are 
tight,  but  drop  out  of  position  if  the  rope  slackens  up,  and  in 
dropping  they  release  a  lever  which  holds  the  weight  seen  under 
the  hand  rope  sheave.  The  movement  of  this  lever  operates  a 
catch  that  engages  with  the  hand  rope  sheave  and  thus  the  hori- 
zontal bar  that  operates  the  brake  and  the  controller  switch  is 
brought  to  the  stop  position  and  the  rotation  of  the  hoisting  drum 
is  stopped. 

The  hand  rope  has  fastened  to  it  at  the  top  and  bottom  of  the 
elevator  shaft  stops  that  are  moved  by  the  car  when  it  reaches 
either  end  of  its  travel,  and  thus  the  elevator  machine  is  stopped 
automatically.  This  arrangement  is  the  same  as  that  used  with 
the  belt  driven  machines  already  described,  but  as  an  additional 
safety,  a  stop  motion  is  provided  on  the  machine  itself,  so  that  if 
the  stops  on  the  hand  rope  become  displaced,  the  car  will  still  be 
stopped  automatically  at  the  top  and  bottom  landings.  This  stop 
motion  is  seen  on  the  end  of  the  shaft,  just  in  front  of  the  hand 
rope  sheave,  and  consists  of  a  nut  that  travels  on  the  shaft  as  the 
latter  revolves.  At  both  sides  of  the  screw  there  are  projection 
cases  upon  the  inclosing  frame,  which  are  struck  by  the  traveling 
nut  when  it  comes  near  enough  to  either  end.  When  the  nut 
strikes  the  projection,  the  hand  rope  sheave  is  revolved  with  the 
shaft  and  thus  the  machine  is  stopped.  To  understand  this  ac- 
tion it  must  be  remembered  that  the  hand  rope  sheave  does  not 
revolve  except  when  turned  by  the  pull  on  the  hand  rope  or  by 
the  action  of  the  slack  cable  stop  or  the  traveling  nut. 

The  controller  box  on  top  of  the  motor  contains  the  starting 
resistance,  the  starting  and  reversing  switch,  and  also  a  magnet 
to  actuate  a  switch  that  gradually  cuts  out  the  starting  resistance. 
The  way  in  which  the  switches  act  to  start  and  stop  the  motor 
can  be  readily  explained  by  the  aid  of  the  diagram  Fig.  7. 

This  shows  the  circuit  connections  ia  the  simplest  possible 


734  HANDBOOK    ON    ENGINEERING. 

form.     In  this  diagram  all  the  wires  whose  presence  would  make 


SAFETY  MAGNET  FOR 
BRAKE  ON  MACHINE 


SHUNT  FIELD 

the  drawing  confusing  have  been  removed,  but  the  manner  in 


HANDBOOK    ON    ENGINEERING.  735 

which  they  are  connected  will  be  readily  understood  from  the 
following  explanation :  — 

The  main  switch,  which  connects  the  motor  circuits  with  the 
line,  is  located  at  the  upper  left  hand  corner  of  the  diagram,  the 
main  line  wires  being  marke  -|-  and  —  .  When  this  switch  is 
closed,  the  motor  circuits  are  connected  with  the  line,  but  the 
motor  circuit  itself  is  not  closed  so  long  as  the  switch  M  remains 
in  the  position  shown.  When  this  switch  is  turned  about  one 
quarter  of  a  revolution  in  either  direction,  one  end  will  ride  over 
the  upper  contact  and  the  other  one  over  the  lower  contact. 
The  reversing  drum  and  switch  M  are  mounted  on  the  same 
spindle  and  move  together.  They  are  located  within  the  con- 
troller box,  on  top  of  the  motor,  and  are  moved  by  the  horizontal 
bar  ;  see  Fig.  6.  The  shaded  portions  of  the  drum,  on  which  the 
brushes  h  and  i  rest  are  made  of  insulating  material  so  that  when 
switch  M  and  the  reversing  drum  are  in  the  position  shown  the 
motor  circuit  is  open  at  two  points.  This  is  the  position  of  these 
parts  when  the  machine  is  stopped. 

The  starting  resistance  is  shown  above  the  reversing  drum, 
and  in  the  machine  it  occupies  the  space  at  the  back  of  the  con- 
troller box,  shown  on  top  of  the  motor  in  Fig.  6.  The  segment 
R  is  a  series  of  contacts  that  are  connected  with  the  resist- 
ance in  the  resistance  box ;  No.  2  contact  being  con- 
nected with  point  2  on  the  resistance  and  so  on  for  all  the  other 
numbers.  The  switch  arm  N  is  moved  over  the  contacts  R  by  a 
magnet  that  is  represented  by  the  spiral  L.  The  motor  arma- 
ture and  the  shunt  and  series  field  coils  are  shown  at  the  bottom 
of  the  diagram.  The  motor  is  compound  wound,  it  being  made 
so  for  the  purpose  of  keeping  the  starting  current  as  low  as  possi- 
ble. The  path  of  the  current  through  the  wires  is  as  follows  :  Sup- 
pose the  reversing  drum  and  the  M  switch  are  revolved  in  the  direc- 
tion in  which  the  hands  of  a  clock  move,  then  brushes  g  and  i  will 
rest  on  one  segment,  and  h  and  k  will  rest  on  the  other  segment. 


736  HANDBOOK    ON    ENGINEERING. 

As  switch  M  will  now  be  closed,  the  current  will  flow  to  brush 
g  and  through  the  reversing  drum  segment  to  brush  i;  then  it 
will  follow  the  wire  to  the  right  side  /of  the  armature  and  pass- 
ing through  the  latter  will  reach  wire  E  and  thus  brush  ft,  from 
which  it  will  pass  to  brush  ~k.  From  this  brush  the  current  will 
go  to  and  through  magnet  L  and  by  wire  C '  and  switch  N  will 
reach  contact  No.  10.  As  this  contact  is  connected  with  point 
10  of  the  resistance  the  current  will  reach  the  latter  and  will  pass 
through  the  whole  of  it,  coming  out  at  the  opposite  end  C.  This 
end  is  connected  with  contact  C,  so  that  from  this  segment  the 
current  can  flow  through  wire  G  to  the  end  F  of  the  series  field 
coils,  and  passing  through  these  to  end  H,  will  find  its  way  to 
wire  /,  and  thus  return  to  the  opposite  side  of  the  main  line. 
From  this  explanation  it  will  be  seen  that  the  current  will  pass 
through  the  motor  armature,  and  then  through  the  whole  of  the 
resistance  in  the  resistance  box,  and  then  through  the  series  field 
coils,  and  finally  reach  the  other  side  of  the  main  line.  From 
the  switch  M  another  current  will  branch  off  and  run  to  binding 
post  D,  and  thence  through  the  shunt  field  coil  to  binding  post 
JTand  thus  to  wire/,  and  through  the  latter  to  the  opposite  of 
the  main  line. 

The  switch  lever  ^V  is  in  some  cases  arranged  so  that  the  mag- 
net L  acts  to  hold  it  upon  contact  10  and  a  spring  acts  to  carry 
it  forward  toward  contact  A;  in  other  cases  the  magnet  is  wound 
with  two  coils,  one  of  which  pulls  N  in  one  direction  and  the 
other  pulls  it  in  the  opposite  direction,  the  two  coils  being  so  pro- 
portioned that  N  moves  gradually  from  contact  10  toward  con- 
tact A.  If  we  take  the  spring  arrangement,  then  magnet  L  will 
pull  N  back  toward  contact  10,  and  the  spring  will  pull  it  forward. 
As  the  starting  current  is  very  strong,  ^will  be  held  on  contact 
10,  but  as  the  current  weakens,  the  spring  will  begin  to  overpower 
the  magnet,  and  N  will  slide  oVer  contact  9  and  then  8  and  7  and 
so  on  to  contact  A.  As  contact  9  is  connected  with  the  point  9 


HANDBOOK    ON    ENGINEERING.  737 

of  the  resistance,  when  JV  reaches  it,  the  section  of  the  resistance 
between  points  10  and  9  will  be  cut  out.  When  N  reaches  con- 
tact 7  the  resistance  between  points  10  and  7  will  be  cut  out  for 
the  latter  point  is  connected  with  contact  7.  As  all  the  contacts 
are  connected  with  the  corresponding  points  of  the  resistance, 
when  N  reaches  contact  C,  all  the  resistance  in  the  resistance  box 
will  be  cut  out  of  the  circuit.  As  will  be  noticed,  contact  B  is 
connected  with  the  center  point  G  of  the  series  field  coil  so  that 
when  N  reaches  contact  B  one-half  of  the  series  coils  will  be  cut 
out  in  addition  to  the  whole  of  the  resistance  box.  When  N 
reaches  contacted  the  current  will  pass  directly  to  wire/,  and  thus 
cut  out  all  the  series  field  coils  and  then  the  motor  will  run  as  a 
plain  shunt- wound  machine,  and  its  speed  will  be  the  highest  it 
can  attain. 

If  the  reversing  drum  and  switch  M  are  now  revolved  to  the 
position  shown  in  the  diagram,  the  circuit  through. the  motor  will 
be  broken  and  the  machine  will  come  to  a  state  of  rest.  If  the 
reversing  drum  and  M  are  now  revolved  in  the  opposite  direction, 
that  is,  contrary  to  the  movement  of  the  hands  of  a  clock,  the 
brushes  g  and  h  will  rest  on  one  of  the  revolving  drum  segments, 
and  i  and  k  on  the  other  segment.  If  the  path  of  the  current  is 
now  traced  it  will  be  found  that  it  will  enter  the  armature  through 
wire  E,  and  the  left  side,  instead  of  through  wire  /,  as  in  the  pre- 
vious case.  It  will  also  be  found,  however,  that  the  current  after 
passing  through  the  armature  will  reach  the  series  field  coils 
through  F,  which  is  the  same  path  as  before,  so  that  the  direction 
of  the  current  has  been  reversed  through  the  armature  only, 
which  is  what  is  required  to  reverse  the  direction  of  rotation  of 
the  motor.  Whichever  way  the  switch  M  and  the  reversing  drum 
are  turned,  the  direction  of  the  currents  through  the  series  field 
coils  and  the  shunt  field  coil  will  be  the  same,  and  only  the  arma- 
ture current  will  be  reversed. 

Cutting  out  the  series  field  coils  not  only  increases  the  speed 

47 


738  HANDBOOK    ON    ENGINEERING. 

of  the  motor,  but  obviates  the  danger  of  the  car  attaining  a  dan- 
gerously high  speed  if  the  load  is  being  lowered.  A  shunt  wound 
motor  will  run  as  a  motor  up  to  a  certain  speed,  but  if  the  veloc- 
ity is  forced  above  this  point  by  driving  the  machine  by  the  ap- 
plication of  external  power,  then  the  motor  will  begin  to  act  as  a 
generator,  and  as  it  takes  power  to  run  a  generator  the  motor  will 
begin  to  hold  back.  Now  if  an  elevator  car  is  running  down 
with  a  heavy  load,  the  load  will  draw  the  car  down,  and  unless  a 
resistance  of  some  kind  is  interposed,  the  speed  will  become 
greater  and  greater  as  the  car  descends,  and  by  the  time  it 
reaches  the  bottom  of  the  shaft  it  may  be  running  at  a  velocity 
almost  equal  to  that  attained  by  a  free  fall.  The  power  required 
to  drive  the  motor  when  acting  as  a  generator  serves  to  hold  the 
car  back,  for  the  current  developed  increases  very  rapidly  with 
increase  of  speed,  so  that  an  increase  of  speed  of  ten  or  fifteen 
per  cent  above  the  normal  running  velocity  will  be  about  as  much 
as  can  be  reached  even  with  an  extra  heavy  load. 

Although  the  motor  will  act  as  a  generator  and  hold  the  car  so 
that  it  cannot  attain  a  dangerous  speed  when  descending  under 
the  influence  of  a  heavy  load,  it  will  only  accomplish  this  result 
when  the  circuit  is  closed  ;  for  if  the  circuit  is  open  there  will  be 
no  power  generated ;  hence,  no  power  will  be  absorbed  by  the 
motor.  As  can  be  readily  seen,  it  is  possible  for  the  circuit  out- 
side of  the  motor  to  become  broken  by  the  melting  of  a  fuse  or 
some  other  cause,  and  if  this  occurs  when  the  car  is  coming  down 
with  a  heavy  load  there  might  be  a  serious  accident.  To  obviate 
such  mishaps  the  main  switch  is  made  with  a  magnet  b  which 
holds  the  switch  closed  so  long  as  current  passes  through  it.  but 
allows  the  switch  to  swing  open  if  the  line  current  disappears. 
This  switch  on  this  account  is  called  a  potential  switch,  because 
it  is  arranged  to  be  actuated  by  the  difference  of  potential  be- 
tween the  two  sides  of  the  line.  When  the  line  current  fails,  and 
the  potential  switch  opens,  the  blade  m  comes  ink)  contact  with  n 


HANDBOOK    ON    ENGINEERING.  739 

and  thus  the  circuit  for  the  motor  armature  is  closed  through  the 
resistance  wire  s  which  is  connected  with  contact  7.  This  con- 
nection short  circuits  the  armature  through  a  resistance  sufficient 
to  keep  it  from  being  burned  out,  but  not  enough  to  prevent  the 
motor  from  acting  as  a  brake  and  holding  the  car  down  to  a  safe 
speed. 

The  wire  c  c  which  runs  from  magnet  b  of  the  potental  switch, 
it  will  be  noticed,  connects  with  a  coil  marked  safety  brake  mag- 
net. This  magnet  acts  normally  to  hold  the  brake  off  when  the 
machine  is  running,  but  if  the  current  passing  through  it  dies  out, 
then  it  acts  to  put  the  brake  on.  Now,  as  has  already  been  ex- 
plained, when  the  current  is  flowing  in  the  main  line,  there  is  a 
current  passing  through  coil  b  of  the  potential  switch ;  hence, 
there  is  a  current  passing  through  the  coil  of  the  safety  magnet  for 
the  brake ;  but  if  the  line  current  fails  the  current  through  the 
brake  magnet  will  also  fail  and  the  brake  will  go  on  ;  so  that  the 
car  will  be  doubly  protected,  one  protection  being  the  short  cir- 
cuiting of  the  motor  circuit  through  wire  s,  and  the  other  the  ap- 
plying of  the  brake  by  reason  of  the  failure  of  the  current  to  flow 
through  the  safety  brake  magnet. 

As  to  directions  for  the  proper  care  of  these  machines,  very 
little  need  be  said,  as  they  are  simple  and  substantial  in  con- 
struction and  give  very  little  trouble.  The  motor  proper  requires 
the  same  attention  as  is  given  to  any  stationary  motor,  that  is, 
the  commutator  and  all  other  parts  must  be  kept  as  clean  as  pos- 
sible and  the  brushes  must  be  properly  set.  As  to  the  other 
parts,  all  that  need  be  said  is  that  the  bearings  must  be  well  lubri- 
cated and  free  from  grit.  They  must  be  tight  enough  to  not  al- 
low the  parts  to  play,  but  at  the  same  time  care  must  be  taken 
that  they  are  not  so  tight  as  to  heat  up  or  cut.  All  bolts  and 
nuts  must  be  re*gularly  examined  and  kept  tight,  so  that  they 
may  not  work  loose  or  out  of  place.  The  most  important  point 
to  observe,  however,  is  not  to  undertake  under  any  circumstances 


740  HANDBOOK    ON    ENGINEERING. 

to  tinker  with  the  sheave  wheel  and  the  gears  that  connect  it  with 
the  horizontal  bar  that  operates  the  brake  and-  controller 
switches.  Neither  must  the  brake  or  the  switches  be  disturbed. 
All  that  is  to  be  done  to  the  latter  is  to  keep  the  contacts  bright 
and  clean.  If  any  of  these  parts,  from  the  sheave  wheel  to  the 
controller  switches,  get  out  of  set,  so  that  the  machine  will  not 
run  satisfactorily,  do  not  undertake  to  readjust  them,  but  send 
for  an  expert  from  the  elevator  company.  If  any  of  these  parts 
are  removed  or  shifted  there  is  danger  of  their  not  being  put 
back  in  their  proper  position,  and  if  they  are  misplaced  a  very 
serious  accident  may  be  the  result.  If  the  proper  adjustment  of 
these  parts  is  destroyed,  the  elevator  will  not  stop  automatically 
at  the  top  and  bottom  landings,  but  will  run  too  far  at  one  end 
and  stop  short  of  the  mark  at  the  other ;  hence,  the  car  may 
either  strike  violently  against  the  floor  or  run  at  full  speed  into 
the  overhead  beams,  and  in  either  case  the  results  might  be  very 
serious.  Even  elevator  experts  have  to  go  cautiously  in  adjust- 
ing the  position  of  the  sheave  wheel  and  the  parts  connected 
with  it. 

The  fact  that  those  not  thoroughly  posted  in  the  operation  of 
these  elevators  should  not  tamper  with  the  hand  rope  sheave  and 
its  connections,  is  not  at  all  unfortunate,  for  it  is  next  to  impos- 
sible for  them  to  get  out  of  place ;  but  special  caution  is  advised 
at  this  point,  because  there  are  many  men  who  are  apt  to  take  it 
for  granted  that  if  the  machine  runs  poorly  from  some  trifling 
cause  that  they  have  not  been  able  to  locate,  the  trouble  must  be 
due  to  some  defect  in  the  adjustment  of  the  several  parts  of  the 
operating  sheave  and  its  connections.  They  will  then  proceed  to 
pull  the  machine  apart,  and  when  they  put  it  together  again  they 
are  very  liable  to  get  it  connected  wrong,  and  if  such  should  be 
the  case  the  first  trip  made  by  the  elevator  might  end  seriously. 

Although  the  machine  described  in  the  foregoing  works  in  an 
entirely  satisfactory  manner,  it  has  been  superseded  almost  en- 


HANDBOOK    ON    ENGINEERING. 


741 


tirely  in  first-class  installations  of  recent  date  by  machines  that 
are  controlled  by  means  of  a  small  switch  in  the  car  instead  of 
the  hand  rope.  There  are  several  types  of  such  elevators  made 
by  the  Otis  Company,  one  of  the  latest  designs  being  shown  in 
Fig.  8. 


Fig.  8. 

As  will  be  noticed  at  once,  this  machine  is  different  in  several 
respects  from" the  hand  rope  control  machine  shown  in  Fig.  6.  As 
the  machine  is  controlled  by  the  movement  of  a  switch  in  the  car, 
the  brake  cannot  very  well  be  actuated  mechanically,  hence  a 
magnetic  brake  is  provided,  the  magnet  being  seen  at  the  top  of 
the  stand  to  the  right  of  the  motor.  The  automatic  stopping  de- 
vices and  the  slack  cable  stop  are  also  arranged  so  as  to  act  upon 


U  \MMUH   K     ON 


:u<-.  \\lr  uM  \vithm  tlu  -  8<»«  ftt  tho  ftvnt 

OTul      i^f  UU,       Tt^    t>^  of 

iu«ohino  N  tu  on  top  of  thfc  moliWr*  g^nv 


is  not  ooumvuM  nuvhHnXonll^v  with  HUV  of  llie  movii^r  jvirts  v^f  UM 
.   U   OHU  IH>  Uvntxxi  HI  auv  vvu\vi\iout  |K>iut,  *«vl  is  then 
with  tho  motor  artii&turv.  tioUt  o\>ils  aiul  with  tho  I 


11  VMMIOOK     ON      l\\t,lM    t    IM\  748 

magnet    and    automatic   stop   switches   \\\    moans  of    oopp.  i    \\ 
Pho    controller   used    \\ilh    this  t\pe   of   maehino  is  arranged   alter 
I  ho    fashion   of   a    switchboard,  the    switches    hoiiuv  located  on  tho 
front..  Mud  the  eonnoelino   vrites,  together  \\ith    the  start  inu  rwist 
.•moo,  hoini;  .'it  I  ho  haek.       Hie  >\\itfi»os   :uv  :u't  u.-Uod  l>\    ini\Mi>->  of 
.  Miui  on  th:il  :uvonnt  llu>  ilo\itv  i-  cMllod   :i  in:i"jn-t 
o  ili:»«vr:un  i>f  llu1  \virinn'  t-oniuMMions  \\ilh  this  i-on- 
(rollor  is  nioro  i'oiuplicMloil  than  tluU  for  llu>  IIMIK!  ro|H>  iionlrolh»r. 
but  for   tlio    jMirposo   i>t    siiuplil  vin^   tho   »lr:i\\  in^  as  nnu    . 
sihlo    1     l»:ivo    iviuovi'il    all     llu1    i-oiiiu'i'tions    that    air    not   actually 
necossaiN    for   a  j>ropt»r  iiiuliM-staiuIin^  of    tlu>  ^MUM-al  arran-MMin'Ml 
of  tho  I'in'iiits.       1'his  simplitiod  diagram  i-  sho\\n    in  V\^.  1>. 

The  front  of  tlu«  i-onlrolU'r  ix  slu»\\n  in  Ki^.  10.  and  tho  l»:u-U 
of  s.'imo  in  Fio;.  11.  tho  starting  rosistanoo  l»oin^  ronio\»>d  in  tlii* 
illustratii>n  so  as  to  atToi'd  a  oU-ar  \io\vof  tho  \\  in>  oonnoot ions. 
Tho  sido  of  tho  starting  n^i-tanoi"  oan  l»o  soon  in  Fii>\  10.  In 
this  la^t  nainod  illn.-t  rat  ion,  all  tho  s\viiclu's  arc1  in  tho  position 
they  tako  \vhon  tho  olo\ator  is  stoppod.  Tho  t\\o  lar^o  s>\iioli»'x 
oniMthor  sido  at  tho  bottom  of  thohoanl  aro  t  ho  starting  s\\  itches. 
one  noting  to  run  tho  oar  up  and  tho  othor  ono  to  run  it  do\\n. 
Tho  t\\o  -inallor  switcho^  oooupx  \\\g  tho  o»-iilor  of  tho  U>Itoni 
panol  of  tho  hoard  ami  the  two  Bitches  in  tho  upper  corner  are 
for  tho  purpose  of  aecelorat \ug  tho  volooitx  of  tho  motor  wlion  it 
is  Started.  'When  tho  motor  starts,  tlioro  is  a  resiM;mce  in  tho 
annatur*'  oiivuit,  ami  the  current,  nfior  passing  through  the  arm:i- 
ture  is  passed  tiirou^h  ^iM'ii's  I'u-ld  coils.  After  tho  motor  has 
started,  the  Martin^  resistance  is  out.  out,  and  then  tho  series  lield 
ooils  are  out  out.  so  that  \\henthofull  speed  is  a'tainod.tho 
motor  is  a  simple  shunt-wound  machine.  In  this  ivspoot  tho 
arrangement  of  tho  motor  circuits  is  the  same  as  in  tho  hand  rope 
controller  maohino. 

When  it  's  desired  to  start  tho  car.  a  small  s\\itch  in  the  latter 
is  moved  ;o\vard  tho  riirht  or  loft .  according  to  1  he  direct  ion  in 


744 


HANDBOOK    ON    ENGINEERING. 


which  the  car  is  to  move.  To  run  the  car  up,  the  car  switch  is 
turned  to  the  left,  and  this  movement  sends  a  current  through  the 
magnet  of  the  lower  right  side  magnet  on  the  controller  board. 


Fig.  10. 

This  magnet  then  lifts  its  plunger  and  the  two  discs  mounted  upon 
the  latter  come  into  contact  with  the  stationary  connectors  located 
just  above  them,  and  then  the  current  can  find  its  way  through 


HANDBOOK    ON    ENGINEERING, 


745 


the  motor  circuits  in  the  proper  direction  to  produce  the  upward 
motion.  The  four  small  switch  magnets  on  the  controller  board 
are  connected  in  separate  circuits  that  are  in  parallel  with  each 


Fig.    11. 

other,  and  in  shunt  relation  to  the  armature  of  the  motor.  When 
the  motor  first  starts,  the  counter  electromotive  force  developed 
by  the  armature  is  not  as  great  as  when  it  is  running  at  full  speed, 


746  HANDBOOK    ON    ENGINEERING. 

because  a  portion  of  the  electromotive  force  of  the  line  current  is 
used  to  force  the  current  through  the  starting  resistance  and 
through  the  series  field  coils.  When  a  portion  of  the  starting 
resistance  is  cut  out  the  armature  counter  electromotive  force  is 
correspondingly  increased.  When  more  of  the  starting  resistance 
is  cut  out,  the  counter  electromotive  force  is  further  increased. 

It  is  still  further  increased  when  the  series  field  coils  are  cut 
out.  Now  the  current  that  passes  through  the  magnets  of  the 
four  small  switches  on  the  controller  board  increases  as  the  counter 
electromotive  force  of  the  motor  armature  increases.  The  mag- 
nets are  so  adjusted  that  as  the  currents  passing  through  them 
increase  one  after  the  other  will  lift  its  plunger  and  then  the  con- 
nections made  by  the  discs  at  the  lower  end  of  these  plungers  will 
cut  out  successively  the  sections  of  the  starting  resistance  and  the 
sections  of  the  series  field  coils.  The  two  small  tubes  at  the  top 
of  the  controller  board  are  safety  fuses,  and  the  line  wires  are 
connected  with  their  upper  ends. 

By  the  aid  of  the  foregoing  explanation  of  the  way  in  which 
the  controller  acts,  the  following  description  of  the  wiring  diagram 
(Fig.  9)  will  be  easily  understood.  In  this  diagram  the  line 
wires  come  in  at  the  top  of  the  controller  and  are  marked  -}-  and 

.  The  motor  is  shown  at  the  bottom  of  the  diagram,  the  circle 

A  representing  the  armature,  and  the  coil  B  is  the  brake  magnet. 
The  stop  motion  switch  is  placed  on  the  elevator  machine,  in  one 
of  the  casings  at  the  front  end  of  the  drum,  and  is  actuated  by 
the  automatic  stop  mechanism  which  stops  the  car  at  the  top  and 
bottom  landings.  The  car  switch  is  shown  in  the  upper  left  hand 
corner  of  the  diagram,  and  the  curved  lines  J  represent  the  wires 
that  connect  it  with  the  motor  and  the  controller  board.  These 
wires  are  placed  within  a  flexible  cable  that  is  attached  to  the 
side  of  the  elevator  shaft  half  the  way  up  from  the  bottom,  the 
cable  being  long  enough  to  reach  the  car  when  at  either  end  of 
the  shaft.  The  limit  switch  in  the  car  is  for  the  purpose  of  stop- 


HANDBOOK    ON    ENGINEERING.  747 

ping  the  motor,  if  the  car  reaches  either  end  of  its  travel  without 
being  stopped  by  the  operator,  or  the  action  of  the  stop  motion 
switch.  This  switch  is  closed  under  ordinary  conditions,  so  that 
the  current  in  wire  C  can  flow  all  the  way  to  the  lower  contact  a 
of  the  car  switch.  If  it  is  desired  to  run  the  car  down,  the  car 
switch  is  turned  to  the  right,  and  then  wire  C  is  connected  with 
wires  D '  and  FD.  The  stop  motion  switch  is  normally  in  the 
position  shown  so  that  the  current  in  wire  D '  can  pass  to  D0  and 
following  this  wire  it  will  reach  contact  DO  which  is  under  the 
lower  disc  of  the  right  side  starting  switch.  Through  the  disc 
this  contact  is  connected  with  the  corresponding  contact  on  the 
other  side  of  the  disc,  and  this  latter  contact  is  connected  with  a 
wire  that  carries  the  current  to  the  magnet  of  the  left  side  starting 
switch.  Considering  now  the  main  current  in  the  +  line  it  can 
be  seen  that  it  can  flow  down  to  the  line  near  the  bottom  of  the 
controller  portion  of  the  diagram,  and  which  terminated  in  the 
-f-  contacts  of  both  the  starting  switches,  but  can  go  no  further 
so  long  as  the  discs  on  the  plungers  of  the  magnets  are  in  the 
lower  position.  As  soon,  however,  as  the  current  coming  from 
the  car  switch  passes  through  the  magnet  of  the  left  side  switch, 
as  just  explained,  the  plunger  will  be  lifted,  and  then  the  disc  will 
connect  the  -f-  contact  with  the  /S2  contact,  and  also  with  a 
smaller  contact  B.  When  this  connection  is  made,  the  main  cur- 
rent can  flow  from  contact  S2  to  contact  $2  of  the  right  side 
switch ,  and  thence  through  the  connecting  disc  to  contact  I  -which 
is  connected  by  wire  .to  binding  post  I;  the  latter  being  con- 
nected with  the  right  side  armature  terminal  I.  After  passing 
through  the  armature  the  main  current  reaches  binding  post  E 
and  through  the  connecting  wire  the  contact  E  at  the  top  of  the 
left  side  starting  switch,  and  as  the  plunger  of  this  switch  is  in 
the  raised  position,  the  current  can  pass  to  contact  R  and  thus 
reach  the  upper  end  R  of  the  starting  resistance  in  the  resistance 
box. 


748  HANDBOOK    ON    ENGINEERING. 

From  the  end  F  of  the  starting  resistance,  the  main  current 
flows  to  binding  post  F  and  then  to  the  F  end  of  the  series  field 
coils,  and  from  end  H  to  binding  post  //  and  to  the  —  line  wire 
at  the  top  of  the  diagram.  The  current  for  the  shunt  field  is 
taken  from  the  contact  S2  at  the  bottom  of  the  left-ride  starting 
switch,  and  passes  to  point  £4  and  thence  to  D  and  to  the  D  end 
of  the  shunt  field  coil,  and  through  this  coil  to  end  //  of  the  series 
coil,  and  thus  to  the  —  line.  The  current  for  the  brake  magnet 
starts  from  the  small  contact  B  at  the  bottom  of  the  left-side 
starting  switch. 

The  car  switch  when  moved  will  first  cover  contact  D'  so  that 
the  main  current  will  follow  the  path  outlined  above,  but  as 
soon  as  the  car  switch  covers  contact  FD,  the  current  passing- 
through  wire  FD  in  the  cable  will  reach  the  stop-motion  switch 
and  pass  to  F,  and  thus  to  magnet  No.  1  at  the  upper  left  hand 
corner  of  the  controller  board.  The  lifting  of  this  switch  will 
cause  its  disc  to  connect  the  contacts  RR'  and  thus  the  current 
will  pass  to  point  R'  of  the  resistance  and  cut  out  the  upper  sec- 
tion. The  current  from  contact  B  at  the  bottom  of  the  left-side 
starting  switch  passes  through  the  magnet  coils  of  the  three 
switches,  Nos.  2,  3  and  4.  Now  soon  after  the  first  section  of 
the  starting  resistance  is  cut  out,  No.  2  magnet  becomes  strong 
enough  to  lift  its  plunger,  and  then  the  current  from  the  right 
side,  contact  R,  at  the  top  of  the  left-side  switch,  will  pass  to 
contact  R  of  No.  2  switch,  and  thus  to  R2  and  to  point  R'2  of 
the  resistance,  thereby  cutting  out  two  sections.  In  this  way  the 
current  through  magnet  of  switch  No.  3  will  be  increased  and  the 
plunger  will  be  lifted  so  that  the  current  will  be  able  to  pass  from 
the  R  contact  of  this  switch  to  the  G  contact,  and  thus  to  binding 
post  G  and  to  the  center  of  the  series  field  coils,  thereby  cutting 
out  one-half  of  these  coils.  In  this  way  the  current  through  coil 
of  No.  4  magnet  will  be  farther  increased,  so  that  it  will  be  able 
to  lift  its  plunger,  and  thus  form  a  direct  connection  from  contact 
G  of  switch  No.  3  and  the  main  wire  leading  to  the  —  line. 


HANDBOOK    ON    ENGINEERING.  749 

Thus  it  will  be  seen  that  the  four  switches,  1,2,  3  and  4,  will 
act  one  after  the  other.  This  same  operation  is  repeated  if  the 
car  switch  is  moved  to  the  right,  so  as  to  run  the  elevator  down, 
the  only  difference  being  that  the  starting  switch  at  the  right  side 
of  the  board  will  be  lifted,  but  the  action  of  the  four  smaller 
switches  will  be  the  same. 

In  addition  to  the  operating  circuits  described  in  the  foregoing 
there  are  wires  that  connect  the  slack  cable  switch  with  the  motor 
circuits  and  other  connections  by  means  of  which  the  elevator  may 
be  run  from  the  controller  board  whenever  desired.  These  con- 
nections are  not  shown  in  Fig.  9,  as  they  would  complicate  the 
drawing,  and  it  is  not  thought  advisable  to  complicate  the  explan- 
ation of  the  main  part  of  the  system  for  the  sake  of  introducing 
the  minor  details. 

This  type  of  electric  control  is  used  for  elevator  building  in- 
stalled in  office  buildings,  and  others  placed  where  the  car  is  oper- 
ated by  a  regular  attendant.  For  private  house  elevators  and  for 
dumb  waiters  it  is  necessary  to  modify  the  controlling  system  so 
that  the  car  may  be  operated  not  only  from  within,  but  also  from 
any  of  the  floors  of  the  building.  It  is  further  necessary  that 
the  circuit  connections  be  such  that  if  the  car  is  operated  from 
any  floor,  it  will  run  to  that  floor,  whether  above  or  below  it,  and 
further,  so  that  if  it  is  being  operated  by  a  person  within  the  car 
it  cannot  be  operated  by  any  one  else  from  any  of  the  landings. 
It  must  also  be  arranged  so  that  if  the  car  is  set  in  motion  from 
any  floor  it  cannot  be  stopped  or  interfered  with  in  any  way  by 
a  person  at  another  floor.  For  the  purpose  of  safety  the  system 
must  also  be  arranged  so  that  the  car  cannot  move  away  from  any 
floor  until  the  landing  door  is  closed.  This  feature  is  necessary 
to  guard  against  people  falling  through  the  open  doorway  into  the 
elevator  shaft.  Although  it  would  appear  difficult  to  accomplish 
all  these  results  without  resorting  to  great  complications,  as  a 
matter  of  fact  the  system  used  by  the  Otis  Company  is  decidedly 


750 


HANDBOOK    ON    ENGINEERING, 


DOOR  CONTACTS 


HANDBOOK    ON    ENGINEERING.  751 

simple.  At  each  floor  of  the  building  a  push  button  is  placed, 
and  by  pressing  this  for  an  instant  the  cur  is  set  in  motion  wher- 
ever it  may  be,  providing  it  is  not  being  used  by  some  other  per- 
son, and  when  it  reaches  the  floor  from  which  it  has  been  operated 
it  will  stop  automatically.  If  the  elevator  is  operated  from  the 
car,  a  button  is  pushed  that  corresponds  to  the  floor  at  which  it 
is  desired  to  stop,  the  car  will  then  begin  to  move,  and  when  the 
floor  is  reached  it  will  stop.  If  the  passenger  after  stepping  out 
of  the  car  forgets  to  close  the  landing  door,  the  elevator  cannot 
be  moved  away  from  the  landing  by  the  manipulation  of  any  of 
the  push  buttons  on  the  various  floors  or  within  the  car.  The 
way  in  which  all  these  results  are  accomplished  can  be  made 
clear  by  the  aid  of  Fig.  12,  which  is  a  simplified  diagram  of  the 
wiring. 

In  this  diagram  most  of  the  parts  are  marked  with  their  full 
name.  The  floor  controller  is  a  drum  which  is  revolved  by  the 
elevator  machine  and  its  office  is  to  shift  the  connections  of  the 
wires  11,  22,  33,  44,  from  one  side  of  the  circuit  DU  to  the 
other  as  the  car  ascends  and  descends  in  the  elevator  shaft.  This 
shifting  of  these  connections  is  necessary  to  cause  the  car  to  run 
down  if  above  the  landing  from  which  it  is  operated,  and  to  run 
up  if  it  is  below  the  landing.  The  actual  position  of  the  floor  con- 
troller with  reference  to  the  elevator  machine  can  be  seen  in  Fig. 
13  in  which  the  floor  controller  is  located  back  of  the  motor  and  is 
driven  from  the  drum  shaft  by  means  of  a  chain  and  sprocket  wheel. 
In  the  diagram  Fig.  12  it  will  be  noticed  that  the  drum  surface  is 
divided  into  two  segments  and  upon  one  rests  the  brush  of  wire 
D  while  upon  the  other  rests  the  brush  of  wire  U.  The  twelve 
contacts  shown  at  G  form  the  operating  switch.  The  center  row 
marked  m  n  o  p  are  movable,  and  the  four  contacts  above  them 
as  well  as  the  four  below  are  stationary.  The  center  row  of  con- 
tacts m  n  o  p  are  moved  upward  by  a  magnet  represented  by  the 
coil  D  and  they  are  moved  downward  by  another  magnet  repre- 


752  HANDBOOK    ON    ENGINEERING. 

sented  by  the  coil  U.  From  this  it  will  be  seen  that  if  a  current 
comes  from  the  floor  controller  through  wire  D  the  movable  con. 
tacts  of  G  will  be  lifted  and  will  connect  with  the  top  row,  while 
if  the  current  comes  from  the  floor  controller  through  wire  £7,  the 
movable  contacts  will  be  depressed  and  will  make  connections  with 
the  lower  row  of  contacts. 

The  main  switch  that  connects  the  motor  circuits  with  the 
main  line  is  shown  at  S.  As  will  be  noticed,  a  wire  marked  d  -{-  II 
runs  from  the  -j-  wire  to  the  right  side  of  the  diagram,  where  the 
landing  and  the  car  push  buttons  and  their  connections  are  shown. 
This  wire  runs  from  top  to  bottom  of  the  elevator  shaft  and  is  con- 
nected with  switches  that  are  closed  when  the  landing  doors  are 
closed,  and  open  when  the  doors  are  open.  These  switches  are 
indicated  by  the  four  circles  marked  door  contacts,  the  diagram 
being  for  a  building  four  stories  high.  If  the  door  contacts  are 
closed,  the  current  can  pass  as  far  as  the  wire  marked  +  which 
runs  through  the  flexible  cable  to  the  car.  In  the  car  there  is  a 
switch  in  this  wire  and  further  on  a  gate  contact,  which  is  closed 
when  the  car  door  is"  closed.  If  these  switches  are  closed,  the 
current  can  return  from  the  car  through  wire  A  and  run  as  far  as 
the  center  of  the  diagram  under  the  main  switch  S.  The  floor 
controller  is  shown  in  the  position  corresponding  to  the  car  at  the 
bottom  of  the  shaft.  Suppose  now  that  the  landing  push  button 
I  is  pressed  for  a  second,  then  the  wires  B  and  I  will  be  connected, 
and  the  current  in  wire  A  will  pass  to  wire  B  and  through  the 
push  button  to  wire  I  and  thence  to  wire  II.  The  coil  between 
wire  I  and  wire  II  is  a  magnet,  and  as  soon  as  the  current  passes 
through  it,  it  draws  the  contact  to  the  right  and  thus  provides  a 
path  for  the  current  direct  from  wire  A  to  wire  M,  so  that  the  push 
button  may  be  raised  without  opening  the  circuit.  The  current 
in  wire  II  will  pass  through  the  floor  controller  to  wire  {/and  thus 
through  magnet  U  of  the  operating  switch  G.  This  magnet  will 
then  draw  down  the  movable  contacts  m  n  o  />,  and  the  main  line 


HANDBOOK   ON   ENGINEERING. 


753 


current  from  the  -f-  wire  will  pass  from  contact  m  to  wire  ra'  and 
through  wiie  m'  to  point  10,  hence  through  wire  w1  to  the  acceler- 
ating, or  starting  resistance,  and  to  wire  F  which  leads  to  th3 
series  field  coils.  Returning  from  these  coils  through  wire  //  to 
magnet  switch  2  and  thence  wire  n'  to  contact  w,  and  as  this  con- 


Fig.   14. 

tact  is  pressing  against  the  one  directly  below  it,  the  current  will 
flow  through  the  connection  to  wire  E  and  thus  to  the  armature ; 
returning  from  the  latter  through  wire  /  and  wire  o'  to  the  contact 
below  o  and  thus  to  o  and  through  the  permanent  connection  to 
contact  p  and  to  the  lower  right  hand  contact  which  is  connected 

48 


754  HANDBOOK    ON    ENGINEERING. 

with  wire  r  which  runs  to  the  —  side  of  the  main  switch.  The 
shunt  field  current  is  derived  from  wire  m'  and  returns  to  contact 
p  and  thus  to  wire  r  through  wire  p' ',  as  can  be  clearly  traced. 
The  brake  magnet  current  starts  from  the  left  side  contact  of  G 
through  wire  -{-  B  and  returns  directly  to  the  lower  end  of 
wire  r. 

The  magnet  switches  1  and  2  act  in  the  same  manner  as  those 
in  diagram  Fig.  9,  that  is,  by  the  increase  in  the  counter  electro- 
motive force  of  the  armature  which  causes  the  current  that  passes 
through  them  to  increase  in  strength.  When  magnet  I  closes  its 
switch,  the  current  passes  from  wire  w'  to  wire  F  and  thus  the 
accelerating  resistance  is  cut  out.  When  magnet  2  closes  its 
switch  the  current  passes  from  wire  m"  directly  to  ri  and  thus  to 
the  armature  without  going  through  the  series  field  coils ;  thus 
the  latter  are  cut  out. 

Returning  now  to  the  operation  of  the  floor  controller  it  will  be 
seen  that  as  the  current  is  flowing  through  wire  II  the  circuit  will 
be  broken  if  the  controller  is  rotated  until  the  gap  at  the  top 
comes  under  the  brush  of  wire  II.  Now  the  floor  controller 
drum  begins  to  turn  as  soon  as  the  elevator  machine  moves,  and 
it  is  so  geared  to  the  elevator  drum  that  when  the  car  comes  op- 
posite the  first  floor  the  brush  of  wire  II  will  be  over  the  upper 
gap,  and  then  the  circuit  will  be  open  and  the  magnet  U  will  be 
de-energized  and  allow  switch  O  to  move  back  to  the  stop  position . 

If  button  No.  4  is  pressed  instead  of  No.  1  the  car  will  not 
stop  until  the  gap  at  the  top  of  the  floor  controller  drum  comes 
under  the  brush  wire  44,  for  the  circuit  between  this  wire  and 
wire  U  will  be  closed  until  that  position  is  reached. 

If  the  car  is  run  up  to  the  fourth  floor,  as  the  gap  at  the  top 
of  the  floor  controller  drum  will  then  be  under  the  brush  of  wire 
44,  the  brushes  of  wire  11,  22  and  33  will  rest  upon  the  same 
segment  as  the  brush  of  wire  D;  therefore,  if  with  the  car  at 
the  top  floor  a  button  is  pressed  at  any  one  of  the  lower  floors 


HANDBOOK    ON    ENGINEERING.  755 

the  current  will  pass  from  its  corresponding  wire  to  wire  D  and 
thus  through  magnet  coil  D  and  to  wire  r'  and  wire  r.  The  cur- 
rent passing  through  magnet  D  will  draw  the  movable  contacts  of 
the  operating  switch  6  upward,  and  thus  set  the  elevator  machine 
in  motion  in  the  opposite  direction  from  that  in  which  it  runs 
when  the  U  magnet  is  energized. 

In  tracing  out  the  circuits  from  the  floor  push  buttons  as  just 
explained  it  will  be  noticed  that  if  any  one  of  them  is  depressed, 
the  current  in  wire  A  will  flow  through  wire  B  to  the  button  de- 
pressed, and  then  enter  the  wire  returning  from  that  button. 
When  the  car  buttons  are  depressed  the  current  in  wire  A  will 
pass  to  wire  C  and  then  through  the  button  in  the  car  to  the 
proper  return  wire ;  that  is,  to  one  or  the  other  of  the  wires 
1,  2,  3,  4.  After  entering  one  of  these  four  wires  the  current 
follows  the  same  path  as  it  does  when  one  of  the  floor  buttons 
is  depressed.  The  magnet  B'  in  the  B  wke,  and  the 
magnet  C'  in  the  C  wire,  are  for  the  purpose  of  preventing  in- 
terference between  a  person  operating  the  elevator  from  within 
the  car  and  another  one  at  one  of  the  landings.  The  B'  switch  is 
actuated  by  a  magnet  that  is  wound  with  two  coils  that  act  in 
opposition  to  each  other.  These  coils  are  shown  to  the  left  of  B' '. 
When  the  elevator  is  operated  from  one  of  the  floor  push  buttons 
the  current  in  wire  A  passes  through  both  the  coils  on  the  magnet 
of  switch  B'  and  as  one  coil  counteracts  the  other  the  switch 
is  left  closed  and  the  current  passes  directly  to  wire  B.  It  the 
elevator  is  operated  from  within  the  car  the  current  from  wire  A 
in  passing  to  wire  C  passes  through  one  of  the  coils  of  the  -mag- 
net that  actuates  switch  B ',  hence  this  switch  is  opened  and  the 
connection  with  wire  B  is  broken,  so  that  if  now  any  one  of  the 
floor  buttons  is  pressed  it  will  have  no  effect  as  the  circuit  is 
opened  at  switch  B'.  The  current  flowing  through  wire  C  passes 
through  a  magnet  that  acts  to  close  the  switch  C'  and  thus  allow 
a  portion  of  the  current  to  pass  directly  to  wire  r.  This  current 


756  HANDBOOK    ON    ENGINEERING. 

will  continue  to  flow  even  after  the  car  has  stopped  at  the  landing, 
providing  the  door  is  not  opened.  As  soon  as  the  door  in  the 
car,  or  the  lauding  door,  is  opened  the  circuit  is  broken  either  in 
wire  Hor  in  wire  A,  and  then  the  car  cannot  be  moved  until  the 
doors  are  closed.  If  it  were  not  for  switch  C'  it  would  be  possi- 
ble for  a  person  at  one  end  of  the  landings  to  move  the  car  if  he 
pressed  the  button  during  the  short  interval  of  time  between  the 
stopping  of  the  car  and  the  opening  of  the  landing  door.  The 
opening  of  the  door  would  stop  the  car,  but  by  this  time  it  might 
be  a  foot  or  two  away  from  the  floor  level.  The  current  that 
passes  from  switch  C'  to  wire  r  is  kept  down  to  a  small  amount 
by  passing  it  through  a  high  resistance  which  in  the  diagram  is 
marked  700  w. 

The  electrical  portion  of  the  Otis  electric  elevators  has  been 
supplied  for  many  years  to  four  or  five  of  the  leading  companies, 
which  were  controlled  by  the  Otis,  and  during  the  last  two  or 
three  years  it  has  been  supplied  to  practically  all  the  prom- 
inent makers,  as  these  are  now  part  and  parcel  of  this 
company ;  hence  the  descriptions  given  in  the  foregoing 
are  more  than  likely  to  cover  any  case  met  with  in 
practice,  for  although  there  are  numerous  small  manufacturers, 
the  sum  total  of  their  elevators  in  use  is  comparatively  small. 
The  only  electric  elevators  in  addition  to  those  described  in  the 
foregoing  that  have  come  into  extensive  use  are  those  made  by  the 
Sprague  Electric  Co. 

These  maehines  are  of  two  different  types,  one  being  the  ordi- 
nary drum  design,  and  the  other  the  screw  machine.  The  drum 
machine  is  similar  in  its  main  features  to  the  same  type  of  ma- 
chine of  other  makers,  and  it  is  only  in  the  minor  details  of  con- 
struction that  any  radical  difference  can  be  noted.  In  the  means 
employed  for  controlling  the  motion  of  the  motor,  however,  there 
is  a  decided  difference.  In  all  the  Sprague  elevators  the  car  is 
controlled  electrically,  hand  rope  control  not  being  used  in  any 


HANDBOOK   ON    ENGINEERING. 


757 


758  HANDBOOK    ON    ENGINEERING. 

case.  The  drum  machines  are  arranged  like  those  of  other  makes, 
so  that  the  motor  is  connected  with  the  main  line  whether  the  car 
is  going  up  or  down,  and  acts  as  a  motor  or  as  a  generator  ac- 
cording to  the  conditions  of  the  load ;  that  is  if  the  load  is  lifted, 
the  machine  acts  as  a  motor,  and  if  the  load  is  lowered,  the  ma- 
chine acts  as  a  generator  and  holds  the  car  back.  With  the  screw 
type  of  machine,  the  arrangement  is  different,  the  motor  acting 
as  such  in  raising  the  load,  but  on  the  descent  the  motor  is  dis- 
connected with  the  main  line  and  acts  as  a  generator,  developing 
a  current  that  circulates  in  a  circuit  formed  by  the  motor  connect- 
ing the  wires,  and  which  is  entirely  independent  of  the  main 
line.  In  the  drum  machine,  when  the  motor  acts  as  a  generator 
in  lowering  a  load,  the  current  it  generates  is  sent  back  into  the 
main  circuit,  and  at  all  times  the  machine  is  connected  with  the 
main  line,  while  with  the  screw  type  the  motor  is  only  connected 
with  the  mainline  when  the  load  is  lifted. 

The  general  appearance  of  the  screw  type  of  Sprague  elevator 
is  shown  in  Fig.  14.  This  illustration  represents  two  machines, 
one  placed  on  top  of  the  other.  In  buildings  where  there  is  an 
abundance  of  floor  space,  the  machines  are  all  set  directly  upon 
the  floor,  but  where  floor  space  is  limited,  they  are  stacked  two, 
three  and  even  four  high. 

As  can  be  clearly  seen  in  Fig.  14,  a  long  screw  is  coupled  to 
the  end  of  the  motor  armature  shaft.  This  screw  threads  through 
a  nut  that  is  mounted  in  a  cross  head  that  carries  a  number  of 
sheaves  around  which  the  lifting  ropes  pass.  At  the  extreme  end 
of  the  machine  other  sheaves  are  mounted,  these  being  held  in 
stationary  supports.  The  sheaves  carried  by  the  cross  head 
travel  from  one  end  of  the  machine  to  the  other  as  the  screw  is 
rotated.  When  they  are  drawn  away  from  the  stationary  sheaves 
the  elevator  car  is  raised,  and  when  they  move  toward  the  sta- 
tionary sheaves  the  elevator  is  lowered.  In  this  respect  the 
action  is  just  the  same  as  in  a  horizontal  cylinder  hydraulic  ele- 
vator. 


HANDBOOK    ON    ENGINEERING, 


759 


Fig.  15, 


HAND    BOOK    ON  ENGINEERING. 

The  nut  carried  by  the  traveling  cross  head  is  so  arranged  that 
when  the  latter  reaches  the  end  of  its  travels  at  either  end  of  the 
screw,  the  nut  is  released  and  then  rotates  with  the  screw  with- 
out moving  the  cross  head.  This  forms  a  perfect  top  and  bottom 
limit  stop,  for  even  if  the  motor  continues  to  run,  the  car  cannot 
be  carried  beyond  the  positions  corresponding  to  the  points  at 
which  the  n"ut  slips  around  in  the  cross  head. 

The  brake  for  holding  the  machine  is  mounted  upon  the  outer 
end  of  the  armature  shaft,  and  can  be  seen  at  Fig.  14  at  the  ex- 
treme right  hand  side.  This  brake  is  actuated  by  a  magnet  that 
releases  it,  and  a  spring  that  throws  it  on.  When  the  current  is 
on,  the  brake  is  lifted  and  when  the  current  is  off  the  brake  goes 
on.  In  this  respect,  the  action  is  the  same  as  in  all  other  electric 
elevators. 

The  operation  of  the  motor  is  controlled  by  a  small  switch  in 
the  car,  which  is  connected  with  the  motor  circuits  by  means  of 
wires  contained  in  a  flexible  cable,  just  like  the  Otis  electrically 
controlled  machines.  The  controller  consists  of  a  main  switch ? 
which  is  moved  by  a  "small  motor  called  a  pilot  motor,  and  a  num- 
ber of  smaller  magnetic  switches  whose  action  will  be  presently 
explained.  All  these  parts  are  mounted  upon  a  switchboard,  and 
present  the  appearance  shown  in  Fig.  15.  The  pilot  motor  and 
main  switch  are  located  at  the  top  of  the  board,  and  the  magnet 
switches  cover  the  space  below,  while  the  starting  and  regulating 
resistance  is  mounted  on  the  back  of  the  board. 

The  complete  wiring  diagrams  for  these  machines  is  decidedly 
complicated  owing  to  the  fact  that  there  are  numerous  switches 
and  devices  whose  office  is  to  afford  additional  safety,  or  to  ren- 
der the  control  more  perfect.  When  all  the  parts  that  are  not 
actually  necessary  to  illustrate  the  system  are  removed,  however, 
the  diagram  becomes  quite  simple  and  can  be  readily  understood. 
Such  a  diagram  is  shown  in  Fig.  16.  This  diagram  shows  the 
motor  together  with  the  screw  and  sheaves,  the  elevator  car,  the 


HANDBOOK    ON    ENGINEERING.  761 

counterbalance,  and  the  operating  switches.  The  wires  marked'  -f- 
and  —  are  connected  with  the  main  line.  The  switch  in  the  car 
is  connected  with  the  controller  by  means  of  four  wires,  marked 
c  b  d  and  s.  The  lower  one  of  these  wires,  marked  s,  is  connected 
with  the  stud  around  which  the  car  switch  swings.  When  the 
car  switch  is  moved  onto  the  upper  contact,  it  connects  wire  s 
with  wire  c  and  then  the  car  runs  up.  When  the  car  switch  is 
moved  down  onto  the  lower  contact,  wire  s  is  connected  with  wire 
d,  and  then  the  car  runs  down.  When  the  car  switch  is  placed  in 
the  central  position  wire  s  is  connected  with  wire  b  and  then  the 
elevator  stops.  The  two  switches  marked  "  up  limit,"  "down 
limit,"  are  for  stopping  the  car  automatically  at  the  top  and  bot- 
tom landings.  Normally  the  up  limit  switch  is  closed  and  the 
down  limit  switch  is  open.  With  these  switches  in  this  position, 
which  is  the  position  in  which  they  are  shown  in  the  diagram,  the 
current  from  the  -f-  wire  can  pass  through  the  up  limit  switch  to 
wire  fc,  and  thence  through  wire  I  to  the  armature  of  the  motor, 
and  then  through  the  field  coils,  and  reach  wire  ra.  It  cannot  go 
beyond  this  point  until  the  switch  C  is  moved.  This  is  the  main 
operating  switch,  which  in  Fig.  15  is  seen  at  the  top  of  the  board, 
the  contacts  being  arranged  in  two  circles.  The  pilot  motor  that 
rotates  the  arm  of  this  switch,  which  is  clearly  shown  in  Fig.  15,  is 
represented  in  this  diagram,  Fig.  16,  at  A.  As  will  be  seen  in 
this  diagram,  this  motor  has  a  field  provided  with  two  magnetizing 
coils,  one  for  the  up  motion,  and  one  for  the  down  motion,  and  in 
addition  it  is  provided  with  a  brake  to  stop  it  quickly  and  hold  it 
when  not  in  use.  The  portion  of  the  diagram  marked  B  is  the 
reversing  switch. 

Let  us  suppose  now  that  the  car  switch  is  moved  upward,  so  as 
to  cause  the  elevator  to  ascend,  then  wire  s  will  be  connected  with 
wire  c.  From  the  -{-  wire  a  current  will  pass  through  wire  a  to  s 
and  thus  to  c,  and  through  magnet  e  of  switch  $,  thus  closing  this 
switch  so  as  to  connect  wires  h  and  i.  The  current  in  wire  c  will 


762 


HANDBOOK    ON    ENGINEERING. 


pass  to  B  and  through  the  connecting  plate  u  will  reach  the  end 
of  the  up  field  coil  of  the  pilot  motor,  and  then  pass  through  the 
armature  of  this  motor,  and  finally  through  the  magnet  that  re- 
leases the  brake.  The  pilot  motor  will  now  rotate  the  reversing 
switch  B  so  that  the  contact  plates  will  jnove  toward  the  left. 
This  movement  will  bring  plate  w  under  the  ends  of  wires  s  and  i, 
thus  permitting  a  current  from  s  to  pass  to  i,  and  as  switch  g  is 


BRAKE  RCLCASC 


3PRAGUE    PRATT  SCREW  ELEVATOR 


closed  this  current  will  reach  wire  h  and  thus  the  magnet  J, 
thereby  lifting  the  plunger  switch  that  closes  the  gap  between 
wire  q  and  the  --  wire.  As  the  arm  of  the  main  switch  C 
moves  with  the  reversing  switch  J3,  this  arm  will  ride  over  the 
contacts  on  the  right  side,  marked  "  t^res."  and  thus  the  current 
from  wire  ra  will  be  able  to  reach  wire  q  after  passing  through  the 
up  resistance. 


HANDBOOK    ON    ENGINEERING.  763 

If  the  car  switch  is  left  on  the  upper  contact,  the  pilot  motor 
will  continue  to  rotate  until  the  arm  of  switch  C  reaches  the  top 
of  the  resistance  contacts,  marked  Full  up.  When  this  point  is 
reached,  the  contact  plate  u  of  the  reversing  switch  B  will  pass 
from  under  wire  c  and  the  terminal  of  the  up  field  of  the  pilot 
motor,  and  then  this  motor  will  stop  rotating. 

If  the  car  switch  is  not  kept  on  the  upper  contact  very  long, 
the  pilot  motor  can  be  stopped  with  the  arm  of  switch  C  at  some 
intermediate  point  on  the  resistance  contacts,  thus  by  the  time 
during  which  the  car  switch  is  kept  upon  the  upper  contact,  the 
amount  of  resistance  cut  out  of  the  motor  circuit  can  be  con- 
trolled and  thereby  the  speed  of  the  car  can  be  controlled. 

In  this  operation  it  will  be  noticed  that  the  motor  is  connected 
with  the  main  line  and  that  the  current  enters  through  the  -f-  wire 
and  passes  out  through  the  —  wire.  If  now  we  turn  the  car 
switch  downward,  the  s  wire  will  be  connected  with  the  d  wire  and 
by  following  the  latter  to  the  reversing  switch  B  it  will  be  seen 
that  through  connecting  plate  v  it  is  connected  with  wire  z  which 
leads  to  the  end  of  the  down  field  of  the  pilot  motor,  thus  setting 
the  latter  in  motion  in  the  opposite  direction  so  as  to  shift  the 
contact  plates  of  B  toward  the  right,  and  at  the  same  time  rotate 
the  arm  of  the  main  switch  C  to  the  left,  thereby  making  contact 
with  the  contacts  of  the  down  resistance.  With  the  arm  of  C  in 
this  position,  it  will  be  seen  that  the  current  in  wire  I  can  flow 
through  the  motor  armature  and  field  and  through  wire  ra  to  the 
arm  of  switch  C  and  through  the  down  resistance  to  wire  n  and 
thus  back  to  wire  Z,  thereby  forming  a  closed  circuit  within  the 
motor  wires  and  connections,  and  disconnected  from  the  main  line 
except  on  the  side  of  the  +  wire.  The  rotation  of  B  causes  the 
connecting  plate  x  to  ride  upon  the  terminals  of  wires  s  and  t,  and 
thus  a  current  is  sent  through  the  brake  magnet  so  as  to  lift  the 
brake,  and  allow  the  elevator  machine  to  run.  When  the  pilot 
motor  moves  the  arm  of  C  so  far  as  to  reach  the  top  of  the  down 


764  HANDBOOK   ON   ENGINEERING. 

resistance,  the  contact  plate  v  of  the  reversing  switch  B  will  pass 
beyond  the  terminals  of  wires  d  and  z,  thus  breaking  the  circuit 
of  the  pilot  motor  and  bringing  the  latter  to  a  stop. 

When  the  reversing  switch  B  is  in  the  stop  position,  as  shown 
in  the  diagram,  the  terminal  of  wire  b  does  not  rest  upon  a  con- 
necting plate  but  when  the  switch  is  rotated  for  the  up  motion,  the 
terminal  of  b  rests  on  plate  v  so  that  if  the  car  switch  is  turned 
to  the  stop  position,  the  current  from  wire  b  will  pass  to  wire 
z  and  thus  reverse  the  direction  of  rotation  of  the  pilot 
motor,  and  return  the  switches  to  the  stop  position.  If 
the  car  is  running  down,  when  the  car  switch  is  turned 
to  the  stop  position,  the  current  from  wire  b  will  pass  to 
wire  z  and  thus  reverse  the  direction  of  rotation  of  the  pilot 
motor,  and  return  the  switches  to  the  stop  position.  If  the  car 
is  running  down,  when  the  car  switch  is  turned  to  the  stop  posi- 
tion, the  wire  b  will  ride  over  the  plate  u  and  thus  the  current 
will  pass  through  the  pilot  motor  through  the  up  field  and  thus 
rotate  the  switches  back  to  the  stop  position.  In  each  case,  as 
will  be  noticed,  whenever  the  current  flows  through  wire  b  it  ener- 
gizes coil  /  and  thus  opens  switch  g.  When  the  car  is  running 
up  the  current  for  the  brake  magnet  passes  from  wire  i  through 
the  switch  which  is  energized  by  the  main  current  flowing  in  wire  q. 
When  the  car  runs  too  far  down,  and  closes  the  down  limit  switch, 
the  motor  circuit  becomes  closed  through  wires  j>,  r  and  &,  thus 
giving  another  path  for  the  current  generated  by  the  motor  arma- 
ture and  thereby  increasing  the  resistance  to  rotation. 

The  controller  for  the  Sprague  drum  machines  is  very  similar 
to  the  one  just  described.  It  is  operated  by  a  pilot  motor,  and 
in  so  far  as  the  controller  switchboard  is  concerned  looks  the 
same.  The  only  -  difference  is  that  rendered  necessary  by  the 
fact  that  in  lowering  as  well  as  in  raising  the  load,  the  motor  is 
connected  with  the  line.  This  requires  a  slight  change  in  some 
of  the  wire  connections. 


HANDBOOK    ON    ENGINEERING  .  765 

The  electrical  parts  of  the  Sprague  elevators  require  very  little 
attention  other  than  to  keep  them  clean  and  all  the  contacts  bright 
and  in  proper  adjustment,  so  that  when  moved  a  good  contact 
may  be  made.  Of  the  mechanical  portion,  the  drum  machines 
require  about  the  same  attention  as  other  machines  of  this  type. 
As  to  the  screw  machines,  the  part  that  requires  most  attention  is 
the  screw  and  the  nut.  As  can  be  readily  understood,  if  the  nut 
were  solid,  the  friction  against  the  screw  would  be  very  great; 
therefore,  to  reduce  this  friction,  the  nut  is  made  so  as  to  carry  a 
large  number  of  friction  balls.  These  run  in  a  groove  cut  in  the 
side  of  a  thread  and  roll  between  the  thread  and  the  screw  and 
the  thread  in  the  nut.  A  tube  is  attached  to  the  nut  to  provide  a 
path  through  which  the  friction  balls  can  pass  from  the  end  of  the 
thread  to  the  beginning,  thus  making  an  endless  path  in  which 
they  move.  As  these  friction  balls  are  subjected  to  a  heavy  pres- 
sure, there  is  more  or  less  danger  of  their  giving  trouble  and  on 
that  account  the  thread  on  the  screw  should  be  carefully  examined 
and  kept  as  clean  and  free  from  grit  as  possible.  Under  favorable 
conditions  these  screws  run  very  well,  the  wear  being  trifling,  but 
in  some  instances  they  are  liable  to  cut  badly,  hence  they  should 
be  closely  watched. 

DIRECTIONS  FOR  THE  CARE  AND  OPERATION  OF  THE 
ELECTRIC  ELEVATORS. 

Whenever  the  attendant  wishes  to  handle  the  machine  to  clean, 
adjust,  repair  or  oil  it,  he  should  see  that  the  current  is  shut  off 
at  the  switch,  and  thus  prevent  all  possibility  of  accident. 

Cleaning.  —  Keep  the  entire  machine  clean.  Clean  the  com- 
mutator and  other  contacts  and  brushes  carefully  with  a  clean 
cloth  and  keep  them  free  from  grease  and  dirt.  If  the  face  of  the 
rheostat  on  which  the  rheostat  arm  brushes  work  becomes  burnt, 
clean  with  a  piece  of  fine  sand-paper  (No.  0),  or  if  necessary  use 


766  HANDBOOK    ON    ENGINEERING. 

a  fine  file.  Keep  all  contacts  smooth.  Try  the  rheostat  arm 
when  cleaning  to  be  sure  that  it  moves  freely  off  contacts. 

Oilingf,  —  Oil  the  drum  shaft  bearings  with  good  heavy  oil. 
Oil  the  worm  and  gear  by  filling  the  chamber  around  them  with  a 
mixture  of  two  parts  of  good  castor  oil  and  one  part  good  cylinder 
oil.  Keep  this  chamber  filled  to  the  top  of  worm  or  mark  on 
gauge  glass,  adding  a  little  each  day  as  it  is  used.  The  end 
thrust  bearings  of  the  machine  are  automatically  oiled  from  this 
chamber.  This  should  be  drawn  off  every  two  or  three  months 
and  replaced  by  fresh  oil.  Oil  the  motor  bearings  with  dynamo 
oil.  These  are  automatically  oiled,  but  should  occasionally  be 
supplied  with  fresh  oil.  Lubricate  the  commutator,  rheostat  face, 
drum  switch  and  contacts  VERY  SPARINGLY  with  a  cloth  moistened 
with  oil.  Care  should  be  taken  not  to  supply  too  much  oil  to 
these  parts.  Keep  the  oil  dash-pot,  if  any,  sufficiently  filled  with 
oil  to  allow  the  rheostat  arm  to  move  quickly  on  to  the  first  con- 
tact and  to  retard  this  movement  beyond  this  contact.  The  best 
oil  for  this  purpose  is  fish  oil,  or  some  thin  oil  that  is  not  readily 
affected  by  changes  in  temperature.  If  an  air  dash-pot  is  used, 
keep  it  slightly  oiled  so  as  to  keep  the  packing  soft.  Keep  all 
parts  of  the  elevator,  including  sheaves,  guides,  cables,  etc.,  clean 
and  well  oiled. 

Operating.  —  Before  switching  the  current  on  to  the  machine,  be 
sure  that  the  operating  lever  is  in  its  central  position.  To  ascend, 
draw  the  lever  the  full  throw  to  the  up.  To  descend,  draw  the  lever 
the  full  throw  to  the  down.  To  run  at  slow  speed,  bring  the  lever 
toward  the  center  according  to  the  speed  desired.  To  stop,  bring 
lever  to  slow  speed  when  within  four  feet  of  landing,  and  to  its 
central  position  when  close  to  it.  In  this  way,  the  operator  can 
make  accurate  stops.  When  starting  (machines  on  which  the 
solenoid  is  used)  if  the  current  is  admitted  to  the  motor  too 
rapidly,  thereby  starting  the  car  with  a  jerk,  or  momentarily  dim- 
ming the  lights  on  the  circuit,  check  the  speed  with  which  the 


HANDBOOK    ON    ENGINEERING.  767 

resistance  is  cut  out  of  the  armature  circuit  by  slightly  easing  off 
the  weight  which  acJbs  in  opposition  to  the  core  of  the  small 
solenoid.  This  solenoid  controls  a  valve  in  the  dash-pot  and 
thereby  regulates  its  speed  in  proportion  to  the  current  passing. 
If  a  governor  starter  is  used  and  the  current  is  admitted  too 
rapidly,  tighten  the  governor  spring  on  the  armature  shaft,  or 
close  the  vent  in  air  dash-pot.  If  the  car  refuses  to  ascend 
with  a  heavy  load,  immediately  throw  the  lever  to  the  center 
and  reduce  the  load,  as  in  all  probability  it  is  greater  than 
the  capacity  of  the  elevator.  If  it  refuses  to  ascend  with 
a  light  load,  throw  the  lever  to  the  center  and  have  the 
fusible  strip  examined.  If,  in  descending,  the  car  should 
stop,  throw  the  lever  to  the  center  and  examine  safeties, 
fusible  strip  and  machine,  and  before  starting,  be  sure  that  the 
cables  have  not  jumped  from  their  right  grooves.  If  the  car 
refuses  to  move  in  either  direction,  throw  the  lever  on  the  center 
and  have  the  fusible  strips  examined.  Never  leave  the  car  with- 
out throwing  the  lever  to  the  center.  If  the  car  should  be  stalled 
between  floors,  it  can  be  either  raised  or  lowered  by  raising  the 
brake  and  running  it  by  turning  the  brake-wheel  by  hand.  Such 
a  stoppage  might  be  caused  by  the  current  being  shut  off  at  the 
station,  undue  friction  in  the  machine,  too  heavy  a  load,  fuses 
burnt  out,  or  a  bad  contact  of  the  switches,  binding  posts  or  elec- 
trical connections.  If  the  car  by  any  derangement  of  cables  or 
switch  cannot  be  stopped,  let  it  make  its  full  trip,  as  the  auto- 
matic stop  will  take  care  of  it  at  either  end  of  the  travel.  The 
bearings  should  be  examined  occasionally  to  insure  no  heating 
and  proper  lubrication. 

General  directions*  —  Have  the  machine  examined  occasionally 
by  someone  well  posted  in  electric  motors  and  elevators.  The 
attendant  should  inspect  the  machine  often.  All  brushes  and 
switches  should  be  sufficiently  tight  to  give  a  good  contact,  but 
no  tighter.  None  of  the  brushes  should  spark  when  in  their 


768  HANDBOOK    OX    ENGINEERING. 

normal  position.  When  the  brushes  become  burnt  dress  with 
sandpaper  or  file,  or,  if  necessary,  replace  with  new  ones.  If 
brushes  spark,  dress  with  sandpaper  or  file  to  a  good  bearing, 
and,  if  necessary,  set  up  springs,  but  do  not  make  the  ten- 
sion such  as  to  interfere  with  their  ready  movement.  Adjust 
commutator  brushes  gradually  for  least  sparking.  These  should 
be  close  to  the  central  position.  Contacts  and  brushes  should 
be  kept  clean  and  smooth  and  lubricated  sparingly.  While 
replacing  a  fusible  strip,  be  sure  that  main  switch  is  open,  and  be 
careful  not  to  touch  the  other  wire  with  your  tool  or  otherwise,  as 
such  contact  would  be  dangerous.  Never  put  in  a  larger  fuse 
than  the  one  burnt.  Inspect  the  worm  and  worm-wheel  occasion- 
ally through  hand-holes  in  casing,  to  see  that  they  are  well  lubri- 
cated, and  that  no  grit  gets  into  the  oil.  They  should  show  no 
wear.  The  stuffing  box  on  the  worm  shaft  should  be  only  tight 
enough  to  keep  the  oil  from  leaking  out  of  the  worm  chamber. 
Be  sure  that  all  parts  are  properly  lubricated,  and  that  none  of 
the  bearings  heat.  To  make  sure  that  the  car  and  machinery  run 
freely,  lift  brake  lever  and  then  rotate  worm  shaft  by  pulling  on 
the  brake  wheel.  The  empty  car  should  ascend  without  any  exer- 
tion. Keep  operating  cables  properly  adjusted.  Open  main 
switch  when  the  elevator  is  not  in  service. 


HANDBOOK    ON    ENGINEERING. 


CHAPTER     XXVI. 

HYDRAULIC   ELEVATORS. 

The  purpose  of  these  pages  is  to  furnish  such  instructions  and 
information  as  will  be  of  use  to  engineers  in  the  handling  of  eleva- 
tor machinery.  To  accomplish  this  end,  cuts  and  sectional  views 
of  cylinders  and  valves  of  the  different  types  of  elevator  machin- 
ery made  by  the  different  elevator  companies,  are  herein  produced, 


so  as  to  make  the  different  elevators  plain  to  the  engineer.  It 
must  be  borne  in  mind  that  the  one  point  of  paramount  impor- 
tance for  the  successful  operation  of  an  elevator  is  proper  care 
and  management  ;  a  lack  of  thorough  knowledge  of  the  machine 
and  lack  of  attention  in  this  respect  shortens  the  life  of  the  ma- 
chine and  often  makes  extensive  repairs  necessary. 

HOW  TO   PACK   HYDRAULIC   VERTICAL   CYLINDER 
ELEVATORS. 


Packing  vertical  cylinder  piston  from  top*  —  Run  the  car 
to  the  bottom  and  close  the  gate  valve  in  the  supply  pipe.  Open 
the  air  cock  at  the  head  of  the  cylinder,  and  also  keep  open  the 

49 


770 


HANDBOOK    ON    ENGINEERING, 


Showing  how  to  set  the  rope  on  the  lever  elevator ;  the  sheave* 
want  to  be  on  the  center  of  the  travel,  as  shown. 


HANDBOOK    ON    ENGINEERING.  771 

valve  in  the  drain  pipe  from  the  side  of  the  cylinder  long  enough  to 
drain  the  water  in  the  cylinder  down  to  the  level  of  the  top  of  the 
piston.  Now  remove  the  top  head  of  the  cylinder,  slipping  it  and 
the  piston  rods  up  out  of  the  way,  and  fasten  there..  If  the  piston 
is  not  near  enough  to  the  top  of  the  cylinder  to  be  accessible,  attach 
a  rope  or  small  tackle  to  the  main  cables  (not  the  counter-balance 
cables)  a  few  feet  above  the  car,  and  draw  them  down  sufficiently 
to  bring  the  piston  within  reach.  Remove  the  bolts  in  the  piston 
follower  by  means  of  the  socket  wrench  .furnished  for  that  pur- 
pose. Mark  the  exact  position  of  the  piston  follower  before  re- 
moving it,  so  that  there  will  be  no  difficulty  in  replacing  it.  On 
removing  the  piston  follower  you  will  find  a  leather  cup  turned 
upwards,  with  coils  of  |-inch  square  duck  packing  on  the  outside. 
This  you  will  remove  and  clean  out  the  dirt ;  also  clean  out  the 
holes  in  the  piston  through  which  the  water  acts  upon  the  cup. 
If  the  leather  cup  is  in  good  condition,  replace  it,  and  on  the 
outside  place  three  new  coils  of  |-inch  square  duck  packing,  being 
careful  that  they  break  joints,  and  also  that  the  thickness  of  the 
three  coils  up  and  down  does  not  fill  the  space  by  J  inch,  as  in 
such  case  the  water  might  swell  the  packing  sufficiently  to  cramp 
it  in  this  space,  thus  destroying  its  power  to  expand.  If  too 
tight,  strip  off  a  few  thicknesses  of  canvas.  Replace  the  piston 
follower  and  let  the  piston  down  to  its  right  position.  Replace 
the  cylinder  head  and  gradually  open  the  gate  valve  in  the  supply 
pipe,  first  being  sure  that  the  operating  valve  is  on  the  down 
stroke  or  it  is  so  the  car  is  coming  down.  As  soon  as  the  air  has 
escaped  before  closing  the  air  cock  to  make  sure  the  air  is  all  out 
of  the  cylinder,  make  a  few  trips,  and  the  elevator  is  ready  to 
run. 

Packing  the  vertical  cylinder  valves*  —  To  pack  the  valve, 
run  the  car  to  the  bottom  and  close  the  gate  valve  in  the  supply 
pipe.  Then  throw  the  operating  valve  for  the  car  to  go  up,  open 
the  air  cock  at  the  head  of  the  cylinder  and  the  valve  in  the  drain 
pipe  at  the  bottom,  and  the  water  will  drain  out  of  the  cylinder. 


772 


HANDBOOK    ON    ENGINEERING* 


SECTION  OF  ELEVATOR    CYLINDER    AND 
VALVE  SHOWING  WORKING  PARTS. 


OTIS  V£RTICAL  HYDRAULIC   PASSENGER  AND  FREIGHT  MACHINE 

A  shows  the  position  of  the  valve  at  rest.    B  shows  the  position  of  the  valve  when  the  car  is  goin 
up  or  hoisting.     C  shows  the  position  of  the  valve  when  the  car  is  coming  down  or  lowering. 


HANDBOOK    ON    ENGINEERING.  773 

When  the  cylinder  is  empty,  reverse  the  valve  for  the  car  to  run 
down,  so  as  to  let  the  water  out  of  the  circulating  pipe.  In  cases 
of  tank  pressure,  where  the  level  of  the  water  in  the  lower  tank  is 
above  the  bottom  of  the  cylinder,  the  gate  valve  in  the  discharge 
pipe  will  have  to  be  closed  as  soon  as  the  water  in  the  cylinder  is 
on  a  level  with  that  in  the  tank,  allowing  the  rest  to  pass  through 
the  drain  pipe  to  the  sewer.  As  soon  as  the  water  has  all  drained 
off,  take  off  the  valve  cap  and  remove  the  pinion  shaft  and  sheave, 
marking  the  position  of  the  sheave  and  the  relation  which  the 
teeth  on  the  pinion  bear  to  the  teeth  on  the  rack  before  removing. 
You  can  now  take  out  the  valve  plunger  and  put  the  new  cup 
leather  packings  on  in  the  same  position  as  you  find  the  old  ones. 
Replace  all  the  parts  as  iirst  found.  Before  refilling  the  cylinder, 
close  the  valves  in  the  drain  pipes,  but  leave  the  air  cock  at  the 
head  of  the  cylinder  open  and  be  careful  that  the  operating  valve 
is  in  position  for  the  car  to  go  down.  Gradually  open  the  gate 
valve  in  the  supply  pipe.  When  the  cylinder  has  filled  with  water 
and  the  air  has  escaped,  close  the  air  cock  and  open  the  gate 
valve  in  the  discharge  pipe. 

Packing  piston  rods.  —  Close  the  gate  valve  in  the  supply  pipe. 
Remove  the  followers  and  glands  to  the  stuffing  boxes  and  clean 
out  the  old  packing.  Repack  with  about  eight  turns  of  i  inch  flax 
packing  to  each  rod,  and  replace  glands  and  followers.  Screw 
down  the  followers  only  tight  enough  to  prevent  leaking. 

Packing  Otis  Vertical  Piston  from  bottom*  —  Remove  the 
top  stop-button  on  hand  rope  and  run  the  car  up  until  the  piston 
strikes  the  bottom  head  in  cylinder.  Secure  the  car  in  this  posi- 
tion by  passing  a  strong  rope  under  the  girdle  or  crosshead  and 
over  the  sheave  timbers.  When  secured,  close  the  gate  valve  in 
the  supply  pipe,  open  the  air  cock  at  the  head  of  the  cylinder,  and 
throw  the  operating  valve  for  the  car  to  go  up.  Also  open  the 
valve  in  the  drain  pipe  from  the  side  of  the  cylinder,  and  from 
the  lower  head  of  the  cylinder,  thus  allowing  the  water  to  drain 


774  HANDBOOK    ON    ENGINEERING. 

out  of  the  cylinder.  When  the  cylinder  is  empty,  throw  the  valve 
for  the  car  to  descend  in  order  to  drain  the  water  from  the  cir- 
culating pipe.  In  case  of  tank  pressure,  where  level  of  water  in 
lower  tank  is  above  the  bottom  of  the  cylinder,  the  gate  valve  in 
the  discharge  pipe  will  have  to  be  closed  as  soon  as  the  water  in 
the  cylinder  is  on  a  level  with  that  of  the  tank,  allowing  the  rest 
to  pass  through  the  drain  pipe  to  the  sewer.  When  the  water  is 
all  drained  off,  remove  the  lower  head  of  the  cylinder,  and  the 
piston  will  be  accessible.  Remove  the  bolts  in  the  piston  follower 
by  means  of  the  socket  wrench,  which  is  furnished  for  that  pur- 
pose. Before  removing  the  piston  head,  mark  its  exact  position, 
then  there  will  be  no  difficulty  in  replacing  it ;  also  be  careful  and 
not  let  the  piston  get  turned  in  the  cylinder,  so  as  to  twist  the 
piston  rods.  On  removing  the  piston  follower,  you  will  find  a 
leather  cup  turned  upwards,  with  coils  of  J  in.  square  duck 
packing  on  the  outside.  This  you  will  remove  and  clean  out  the 
dirt ;  also  clean  out  the  holes  in  the  piston,  through  which  the  water 
acts  upon  the  cups.  If  the  leather  cup  is  in  good  con- 
dition, replace  it  and  on  the  outside  place  three  new  coils  of 
|  inch  square  duck  packing,  being  careful  that  they  break  joints 
and  also  that  the  thickness  of  the  three  coils  up  and  down  does 
not  fill  the  space  by  J  inch,  as  in  such  case  the  water  might  swell 
the  packing  sufficiently  to  cramp  it  in  this  space,  thus  destroying 
its  power  to  expand.  If  too  tight,  strip  off  a  few  thicknesses  of 
canvas.  Replace  the  piston  follower  and  cylinder  head,  and  the 
cylinder  is  ready  to  refill.  Close  the  valves  in  the  drain  pipes, 
leave  the  air  cock  open  at  the  head  of  the  cylinder  and  the  oper- 
ating valve  in  the  position  to  descend,  and  open  gate  valve  in  the 
discharge.  Slowly  open  the  gate  valve  in  the  supply  pipe,  allow- 
ing the  cylinder  to  fill  gradually  and  the  air  to  escape  at  the  head 
of  the  cylinder.  When  the  cylinder  is  full  of  water,  leave  the  air 
cock  open  and  put  the  operating  valve  on  the  center.  The  car  can 
then  be  untied,  the  stop  button  can  be  reset,  and  the  elevator  is 
ready  to  use.  Make  a  few  trips  before  closing  the  air  valve. 


HANDBOOK    ON    ENGINEERING, 


775 


The  above  cut  is  the  Auxiliary  Valve  for  Crane  Hydraulic 
Passenger  Elevators. 

The  operation  of  this  valve  is  explained  as  follows :  D  repre- 
sents  the  supply  inlet ;  E,  the  discharge  outlet ;  F,  the  opening 


776  HANDBOOK    ON    ENGINEERING. 

to  the  cylinder ;  6r,  the  pilot  valve ;  H,  the  pilot  valve  supply 
pipe  to  the  motor  cylinder ;  N  and  J",  the  attachment  by  which 
the  valve  is  operated.  Fig.  1  represents  the  valve  on  centers,  or 
the  car  at  rest  at  any  floor  between  limits  of  travel.  It  will  be 
noticed  in  cut  that  the  plunger  heads  A  and  B  are  on  either  side 
of  the  central  opening.  The  water  is  then  entirely  cut  off  from 
the  machine  and  the  pilot  valve  covers  the  port  C.  To  start  the 
car  up,  water  is  admitted  to  the  cylinder  /through  the  inlet  I). 
This  is  accomplished  by  pushing  on  the  connection  in  which 
opens  the  port  C  in  the  pilot  valve  6r,  allowing  the  water  in  the 
motor  cylinder  I  to  flow  into  the  discharge  E.  The  flow  is  regu- 
lated by  the  screw  K.  The  pressure  in  the  motor  cylinder  I 
being  relieved,  the  valve  plunger  moves  to  the  right  under  the 
difference  in  pressure  upon  the  plunger  A  and  L,  L  being  of 
smaller  diameter  than  A.  Supply  is  thus  admitted  to  the  cylin- 
der through  F.  To  start  the  car  down,  pull  on  the  connection  J. 
The  port  C  in  the  pilot  valve  chest  is  opened,  allowing  water 
from  the  pilot  supply  H  to  flow  into  the  motor  cylinder  7.  The 
pressure  on  head  forces  the  plunger  B  to  move  to  the  left.  Water 
is  thus  allowed  to  pass  out  from  F  to  the  discharge  E.  If  a 
slow  movement  of  the  car  is  desired,  connection  J  is  removed  to 
the  right  or  left  for  either  up  or  down,  and  only  enough  to  open 
the  main  valve  slightly  to  give  the  desired  speed.  This  speed  is 
maintained  by  the  lever  0  being  moved  on  its  fulcrum  P,  thus 
necessitating  the  valve  O-  covering  port  C. 

AUTOriATIC  STOP  VALVE. 

The  stop  valve  M  is  opened  automatically  by  the  machine  as 
the  elevator  starts  from  the  top  or  bottom  landing,  giving  free  flow 
of  water  to  the  cylinder.  As  the  car  reaches  the  upper  or  lower 
limit -of  travel,  the  valve  is  automatically  closed,  so  that  the  car 
stops  gradually  at  the  terminals. 


HANDBOOK    ON    ENGINEERING.  777 

OTIS  GRAVITY  WEDGE  SAFETY. 

J.  Under  the  car  is  a  heavy  hardwood  safety  plank,  on  each 
end  of  which  is  an  iron  adjustable  jaw,  inclosing  the  guide  on 
the  guide  post.  In  this  jaw  is  an  iron  wedge,  withheld  from  con- 
tact with  the  guide  in  regular  duty.  Under  the  wedge  is  a  rocker 
arm,  or  equalizing  bar,  with  one  of  the  lifting  cables  attached 
independently  at  each  extremity.  The  four  lifting  cables,  after 
being  thus  attached,  pass  over  a  wrought  iron  girdle  at  the  top 
of  the  car.  Each  cable  carries  an  equal  strain,  and  the  breakage 
of  any  one  cable  puts  the  load  on  the  other  cables,  which  throws 
the  rocker  out  of  equilibrium  and  forces  the  wedges  on  both  sides 
instantly  and  immovably  between  the  iron  jaws  of  the  safety 
plank  and  the  side  of  the  guides,  stopping  the  car.  It  may  be 
raised  to  any  position  by  the  unbroken  cables,  though  it  cannot 
be  lowered  until  a  new  cable  is  put  on. 

2,  Any  cable  will  always  stretch  before  it  breaks,  which  will 
throw  the  equalizing  safety-bar  out  of  equilibrium  and  force  the 
wedges  on  both  sides  into  position.  No  other  safety  device  will 
give  warning  in  advance. 

CARE  OF  HALE  ELEVATORS. 

Keep  the  guide  springs  on  the  girdle  above,  and  the  safety 
plank  below  the  car  adjusted,  so  that  the  car  will  not  wabble,  but 
not  tight  enough  to  bind  against  guides.  When  cables  are  draw- 
ing alike,  the  equalizing  bars  on  a  passenger  elevator  should  be 
horizontal,  and  the  set  screws  free  from  contact  with  the  finger 
shaft,  but  adjusted  so  that  one  of  them  will  come  in  contact 
with  the  finger  shaft  when  the  equalizing  bar  is  tipped  a  certain 
amount  either  way.  If  the  safety  wedges  should  be  thrown  in, 
or  rattle,  when  descending,  the  cause  would  be  from  the  stretch- 
ing or  breaking  of  one  of  the  cables,  the  action  of  the  governor, 
or  from  weakness  of  either  the  spring  on  the  finger  shaft, 


778  HANDBOOK    ON    ENGINEERING. 

safety-wedge  or  gummy  guides.  In  the  first  case,  if  occa- 
sioned by  the  cable  stretching,  the  cable  should  be  examined 
thoroughly,  and  if  it  shows  weakness,  a  new  one  put  on, 
otherwise,  it  can  be  shortened  up,  as  stated  above.  In  the  sec- 
ond case,  the  car  had  probably  attained  excessive  speed  and  the 
governor  simply  performed  its  proper  function.  In  the  third 
case,  new  springs  should  be  put  on  and  the  guides  kept  clean, 
for  it  often  happens  that  the  guides  are  so  dirty  that  the  springs 
cannot  well  prevent  the  wedges  catching.  All  the  safeties  should 
be  kept  clean  and  in  good  order,  so  that  they  will  quickly  respond 
when  called  upon  to  perform  their  duty.  To  loosen  the  wedges 
when  thrown  in,  throw  the  valve  for  the  car  to  ascend.  If  the 
wedges  are  thrown  in  above  the  top  landing,  remove  the  button 
on  the  hand  cable  and  run  the  car  up  until  the  piston  strikes  the 
bottom  of  the  cylinder.  If  this  is  not  sufficient  to  loosen  the 
wedges,  the  car  will 'have  to  be  raised  by  a  tackle.  Keep  all  nuts 
properly  tightened. 

If  traveling1  or  auxiliary  sheave  bushing  is  worn  so  that  sheave 
binds,  or  the  bushing  is  nearly  worn  through,  turn  it  half  round, 
and  thus  obtain  a  new  bearing.  If  it  has  been  once  turned  put 
in  a  new  bushing.  See  that  the  piston  rods  draw  alike.  If  they 
do  not,  it  can  be  discerned  by  trying  to  turn  the  rods  with  the 
hand,  or  by  a  groaning  noise  in  the  cylinder.  However,  this 
groaning  may  also  be  caused  by  the  packing  being  worn  out,  in 
which  case  the  car  would  not  stand  stationary.  See  that  all 
supports  remain  secure  and  in  good  condition. 

WATER  FOR  USE  IN  HYDRAULIC  ELEVATORS. 

In  hydraulic  elevator  service  little  heed  is  usually  given  to  the 
quality  of  water  with  which  the  system  is  operated.  Much  loss 
of  power  by  friction  and  many  dollars  spent  annually  in  repairs 
can  be  avoided  by  a  little  thought  and  action  on  this  subject.  In 
order  to  prove  the  truth  of  this  statement,  one  has  only  to  obtain 


HANDBOOK    ON    ENGINEERING.  779 

two  samples  of  water,  oue  of  soft  water  and  the  other  of  what  is 
commonly  known  as  hard  water.  For  example,  take  rain  water 
as  the  first  sample  and  water  from  the  well  as  the  second.  Now 
rub  your  hands  briskly  together  while  holding  them  immersed  in 
one,  and  then  in  the  other  of  these  samples.  You  will  instantly 
realize  that  the  quality  of  water  used  in  elevator  service  has  much 
to  do  with  the  efficiency  of  the  hydraulic  machinery.  Water  from 
the  service  pipes  of  the  city  water-works  always  contains  more  or 
less  sand  and  other  gritty  substances,  in  suspension,  and  this  grit 
acts  much  the  same  on  the  packing  and  metal  parts  of  the  appar- 
atus as  does  a  sand  blast.  Some  engineers,  having  realized  the 
evil  effects  of  water  in  the  state  that  it  is  generally  used,  have 
attempted  to  remedy  the  matter  by  replacing  the  water  which  is 
lost  by  leakage  or  evaporation  by  the  addition  of  the  water  which 
is  discharged  from  the  steam  traps  of  the  plant ;  and  as  this  has 
been  distilled,  it  is  almost  chemically  pure  —  thus  the  man  who 
uses  distilled  water  in  an  elevator  system  instead  of  the  water 
containing  grit,  is  simply  getting  out  of  one  difficulty  into 
another. 

It  is  a  well-known  fact  in  chemistry  that  pure  water  is  a  solvent 
for  every  known  substance,  and  will  especially  attack  iron  to  a 
large  degree.  Whenever  it  is  practicable,  the  water  for  elevator 
use  should  be  passed  through  a  filter  to  remove  grit  before 
being  allowed  to  pass  into  the  surge  tank.  In  many  cases, 
however,  it  would  be  difficult  for  the  engineer  to  convince  the 
owner  of  the  advisability  of  buying  and  installing  a  filter  for  this 
purpose.  A  simple  and  somewhat  inexpensive  remedy  is  within 
reach  of  all  —  the  plentiful  use  of  soap  will  obviate  many  of  the 
evil  effects  of  hardness  of  the  water,  will  double  the  life  of  the 
packing,  will  reduce  the  loss  by  friction,  and  will,  to  a  large 
extent,  prevent  the  chattering  of  the  pistons,  making  the  elevators 
run  much  smoother.  In  laboratory  practice,  the  degree  of  hard- 
ness or  softness  of  water  is  determined  by  the  amount  of  pure 


780 


HANDBOOK    ON    ENGINEERING. 


OTIS  DIFFERENTIAL  AND 
AUXILIARY  VALVE. 


HANDBOOK    ON    ENGINEERING.  781 

soap  that  is  necessary  to  mix  with  the  water  to  form  a  lather,  or 
to  precipitate  a  certain  quantity  of  carbonate  of  lime  and  other 
substances.  This  same  action,  on  a  larger  scale,  takes  place 
when  soap  is  introduced  into  an  elevator  tank,  and  while  the  oily 
portion  of  the  soap  forms  an  emulsion  with  the  water,  of  great 
lubricating  properties,  the  gritty  matter  is  precipitated  and  can 
be  gotten  rid  of  through  means  of  a  blow-off  in  the  bottom  of  the 
tank.  The  cheapest  and  most  convenient  form  in  which  to  obtain 
soap  for  this  purpose,  is  the  soap  powder  extensively  manufac- 
tured by  various  firms  and  which  can  be  purchased  for  about  four 
cents  per  pound.  In  a  plant  of  six  elevators,  with  usually  a 
storage  capacity  of  some  8,000  gallons,  it  is  a  good  practice  to 
use  about  twenty  pounds  of  this  soap  each  week.  The  soap 
should  be  at  first  dissolved  in  about  ten  times  its  weight  of  boil- 
ing Water,  and  when  cold  it  will  form  a  stiff  soft  soap.  The 
practice  of  putting  in  the  refuse  oil  collected  from  the  drip  pans  is 
of  little  value ;  it  will  not  mix  with  the  water,  but  floats  on  the 
surface.  It  rarely  gets  low  enough  to  enter  the  suction  pipes  of 
the  pumps,  and  has  little  or  no  tendency  to  precipitate  the  solid 
matter  that  is  held  in  suspension  in  the  water. 

If  car  settles,  the  most  probable  cause  is  that  the  valve  or  pis- 
ton needs  repacking.  If  packing  is  all  right,  then  the  air  valve 
in  the  piston  does  not  properly  seat.  If  the  car  springs  up  and 
down  when  stopping,  there  is  air  in  the  cylinder.  When  there 
is  not  much  air,  it  can  often  be  let  out  by  opening  the  air  cock 
and  running  a  few  trips,  but  when  there  is  considerable  air, 
run  the  car  to  near  the  bottom,  placing  a  block  underneath  for 
it  to  rest  upon,  then  place  the  valve  for  the  car  to  descend. 
While  in  this  position-,  open  the  air  cock  and  allow  the  air  to 
escape.  This  may  have  to  be  repeated  several  times  before  the 
air  is  all  removed. 

Keep  the  cylinder  and  connections  protected  from  frost. 
Where  exposed,  the  easiest  way  to  protect  the  cylinder  is  by  an 


782  HANDBOOK    ON    ENGINEERING. 

air-tight  box,  open  at  the  bottom,  at  which  point  keep  a  gas  jet 
burning  during  cold  weather.  Where  there  is  steam  in  the  build- 
ing, run  a  coil  near  the  cylinder.  Keep  stop  buttons  on  hand  cable 
properly  adjusted,  so  that  the  car  will  stop  at  a  few  inches  beyond 
either  landing,  before  the  piston  strikes  the  head  of  the  cylinder. 
Regulate  the  speed  desired  for  the  car  by  adjusting  the  back  stop 
buttons,  so  that  the  valve  can  only  be  opened  either  way  suffi- 
ciently to  give  this  speed.  Occasionally  try  the  governor  to  see 
that  it  works  properly.  Keep  the  machinery  clean  and  in  good 
order. 

ELEVATOR  INCLOSURES  AND  THEIR  CARE. 

Elevator  inclosures,  while  intended  for  protection  to  passen- 
gers, are  often  carelessly  neglected  and  are  often  a  source  of 
danger,  unless  looked  after  and  taken  care  of  in  a  proper  manner. 
It  is  of  the  utmost  importance  that  no  projection  of  any  kind 
shall  extend  into  the  doorways  for  clothing  of  passengers  to 
catch  on,  thus  endangering  their  lives.  The  door  should  move 
freely  to  insure  their  action  at  the  touch  of  the  operator.  See 
that  all  bolts  and  screws  are  tight,  and  replace  at  once  all  that 
fall  out,  otherwise,  the  doors  and  panels  may  swing  into  the  path 
of  the  elevator  cage  and  be  torn  off,  and  probably  injure  some 
one,  thus  placing  the  owner  liable  to  damages.  Elevator  doors 
that  are  automatic  in  their  closing  are  the  best,  but  all  operators 
should  be  held  strictly  responsible  for  accidents  occurring  from 
the  carelessness  of  leaving  doors  open.  All  inclosures  should  be 
equipped  with  aprons  above  the  doors  to  the  ceiling  and  as  close 
to  the  cage  as  possible,  to  prevent  passengers  from  falling  out  or 
extending  their  person  through  to  be  caught  by  ceilings  or  beams 
in  the  elevator  shaft.  As  a  rule,  proprietors  of  buildings  take  a 
pride  in  keeping  their  inclosures  and  cars  in  a  neat  condition,  as 
they  are  considered  an  ornament  to  the  building  for  the  purpose 
for  which  they  are  intended,  and  no  expense  is  spared  in  the 


HANDBOOK    ON    ENGINEERING. 


783 


line  of  art;  so  it  is  recommended  that  they  be  kept  free  from 
dampness.  Dust  with  a  feather  duster  and  use  soft  rags  for 
cleaning.  Never  use  any  gritty  substance,  soaps  or  oils.  If  they 
become  damaged,  have  the  maker  repair  and  relacquer  them. 

STANDARD  HOISTING  ROPE  WITH  19  WIRES 
TO  THE  STRAND. 


0 

fej 

0 

3 

Diameter. 

Circumfer- 
ence 
in  inches. 

Weight  per 
foot  in  IDS. 
of  rope 
with  hemp 
center. 

Breaking 
strain  in 
tons  of 
2000  IDS. 

Proper 
working 
load  in  tons 
of 
2000  Ibs. 

Circumfer- 
ence of  new 
Manilla 
rope  of 
equal 
strength. 

Minimum 
size  of 
drum  or 
sheave  in 
feet. 

1 

24 

61 

8.00 

74 

15 

14 

13 

2 

2 

6 

6.30 

65 

13 

13 

12 

3 

H 

54 

5.25 

54 

11 

12 

10 

4 

H 

5 

4.10 

44 

9 

11 

84 

5 

14 

41 

3.65 

39 

8 

10 

74 

54 

H 

4| 

3.00 

33 

64 

94 

7 

6 

14 

4 

2.50 

27 

54 

8i 

64 

7 

N 

34 

2.00 

20 

4 

n 

6 

8 

i 

84 

1.58 

16 

3 

66 

5J 

9 

1 

2| 

1.20 

11.50 

24 

$1 

44 

10 

1 

24 

0.88 

8.64 

U 

41 

4 

104 

2 

0.66 

5.13 

14 

31 

34 

104 

A 

U 

0.44 

4.27 

1 

34 

21 

101 

4 

14 

0.35 

3.48 

4 

3 

24 

lOa 

A 

If 

0.29 

3.00 

1 

21 

2 

101 

1 

14 

0.26 

2.50 

4 

24 

14 

Operating  Cable  or  Tiller  Rope,  1  in.  diam.;  |  in.  diam.;  4  in.  diam.; 
I  in.  diam. 

Cables,  and  how  to  care  for  them*  —  Wire  and  hemp  ropes  of 
same  strength  are  equally  pliable.  Experience  has  demonstrated 
that  the  wear  of  wire  cables  increases  with  the  speed.  Hoisting 
ropes  are  manufactured  with  hemp  centers  to  make  them  more 
pliable.  Durability  is  thereby  increased  where  short  bending 


784  HANDBOOK    ON    ENGINEERING. 

occurs.  All  twisting  and  kinking  of  wire  rope  should  be  avoided. 
Wire  rope  should  be  run  off  by  rolling  a  coil  over  the  ground 
like  a  wheel.  In  no  case  should  galvanized  rope  be  used  for 
hoisting  purposes.  The  coating  of  zinc  wears  off  very  quickly 
and  corrosion  proceeds  with  great  rapidity.  Hoisting  cables 
should  not  be  spliced  under  any  circumstances.  All  fastenings 
at  the  ends  of  rope  should  be  made  very  carefully,  using  only 
the  best  babbitt.  All  clevises  and  clips  should  fit  the  rope 
perfectly.  Metal  fastenings,  where  babbitt  is  used,  should  be 
warmed  before  pouring,  to  prevent  chilling.  Examine  wire  ropes 
frequently  for  broken  wires.  Wire  hoisting  ropes  should  be  con- 
demned when  the  wires  (not  strands)  commence  cracking.  Keep 
the  tension  on  all  cables  alike.  Adjust  with  draw-bars  and  turn- 
buckles  provided. 

Leather  cup  packings  for  valves*  —  Leather  for  cups  should 
be  of  the  best  quality,  of  an  even  thickness,  free  from  blemish 
and  treated  with  a  water-proof  dressing.  The  cups  should  be 
of  sufficient  stiffness  to  be  self-sustaining  when  passing  over  per- 
forated valve  lining  When  ordering  cups,  the  pressure  of  water 
carried  should  be  specified,  as  the  stiff  cups  intended  for  high- 
pressure  would  not  set  out  against  the  valve  lining  when  low  pres- 
sure is  used. 

Water*  —  Water  for  use  in  hydraulic  elevators  should  be  per- 
fectly clear  and  free  from  sediment.  A  strainer  should  be  placed 
on  the  supply  pipe  and  water  changed  every  three  months,  and 
the  system  washed  and  flushed.- 

Closing  down  elevators*  —  If  an  elevator  is  to  be  shut  down 
for  an  indefinite  period,  run  the  car  to  the  bottom  and  drain  off 
the  water  from  all  parts  of  the  machine ;  otherwise,  a  freeze  is 
likely  to  burst  some  part  of  the  machinery.  If  the  machine  is  of 
the  horizontal  type,  grease  the  cylinder  with  a  heavy  grease  ;  if 
vertical,  the  rods  should  be  greased.  Oil  cables  with  raw  linseed 
oil. 


HANDBOOK    ON    ENGINEERING.  785 


LUBRICATION    FOR   HYDRAULIC   ELEVATORS. 

The  most  effectual  method  of  lubricating  the  internal  parts  of 
hydraulic  elevator  plants  where  pump  and  tanks  are  used,  is  to 
carry  the  exhaust  steam  drips  from  the  foot  of  the  pump  exhaust 
pipe  to  the  discharge  tank,  thus  saving  the  distilled  water  and 
cylinder  oil.  This  system  is  invaluable  when  water  holding  in 
solution  minerals  is  used,  as  these  minerals  greatly  increase  cor- 
rosion. Horizontal  machines  operated  by  city  pressure  are  best 
lubricated  with  a  heavy  grease  applied  either  mechanically  or  by 
means  of  a  piece  of  waste  on  the  end  of  a  pole.  The  former 
method  serves  as  a  constant  lubricator,  while  in  the  latter  case, 
greasing  is  often  neglected,  and  in  consequence  packing  lasts  but 
a  short  time. 

Lubrication  of  worm  gearing*  —  Oils  with  a  body,  such  as 
cylinder  and  castor  oils,  are  best  suited  to  the  purpose.  A  com- 
position of  two  parts  castor  to  one  part  cylinder  oil  of  the  very 
best  quality,  makes  a  desirable  lubricant,  for  the  following  rea- 
sons :  cylinder  oil  being  heavy  with  ample  body,  on  becoming 
warm  runs  freely  to  the  point  of  contact  between  the  worm  and 
the  gear  and  lubricates  readily.  On  the  other  hand,  castor  oil 
when  cool,  or  only  slightly  warm,  retains  its  body  and  makes  an 
excellent  lubricant.  Upon  becoming  heated,  castor  oil  thickens, 
thus  rendering  it  objectionable.  By  the  combination,  efficient 
lubrication  is  obtained  at  all  temperatures. 

Lubrication  of  cables*  —  A  good  compound  for  preservation 
and  lubrication  of  cables  is  composed  of  the  following :  Cylinder 
oil,  graphite,  tallow  and  vegetable  tar,  heated  and  thoroughly 
mixed.  Apply  with  a  piece  of  sheepskin  with  wool  inside.  To 
prevent  wire  rope  from  rusting,  apply  raw  linseed  oil. 

Lubrication  of  guides*  —  Steel  guides  should  be  greased  with 
good  cylinder  oil.  Grease  wood  strips  with  No.  3  Albany  grease 
or  lard  oil.  Clean  guides  twice  a  month  to  prevent  gumming. 

50 


786  HANDBOOK    ON    ENGINEERING. 

Lubrication  of  overhead  sheave  boxes*  —  In  summer  use  a 
heavy  grease.  In  winter,  add  cylinder  oil  as  required. 

BELTS  AND  HOW  TO  CARE  FOR  THEM. 

The  work  required  of  an  elevator  belt  is  most  severe  and  we 
might  say  extraordinary  character,  running  as  it  does  over  a  jarge 
to  a  small  pulley  and  beneath  an  idler,  so  situated  as  to  giv3  the 
small  pulley  as  much  belt  surface  as  possible.  The  belt  runs 
forward  and  backward  as  the  cage  descends  and  ascends,  thereby 
causing  a  certain  amount  of  slip.  It  is  imperative  that  a  belt 
performing  such  service  should  be  of  the  very  best  quality.  The 
following  are  the  specifications :  The  stock  should  be  strictly 
pure  oak-tanned,  cut  in  such  a  manner  that  the  center  of  the  hide 
will  form  the  center  of  the  belt.  Each  piece  should  have  all 
stretch  thoroughly  removed.  The  belt  should  be  short  lap,  none 
of  the  pieces  to  exceed  4'  2"  in  length,  including  the  laps.  Lock 
lap  should  be  made,  which  makes  a  perfect  splice.  Under  no 
circumstances  should  a  straight  lap  be  used.  The  cement  should 
be  of  the  very  best  quality  and  pliable  to  such  an  extent  that  it 
will  allow  for  the  short  turn  taken  by  the  belt  in  passing  under 
the  idler  and  around  the  small  pulley.  As  a  precaution  against 
laps  coming  apart  from  accident  or  other  cause,  belts  should  be 
riveted,  as  the  rivets  will  hold  lap  together  until  defect  may  be 
seen  and  remedied.  Owing  to  the  high  speed,  laced  belts  should 
never  be  used,  as  the  laces  are  sure  to  be  cut  by  running  over  the 
small  pulleys.  Castor  oil  makes  a  very  reliable  dressing  for 
belts.  It  renders  them  pliable,  thus  improving  the  adhesive 
qualities. 

USEFUL  INFORMATION. 

To  find  leaks  in  elevator  pressure  tanks  in  which  air  is  con- 
fined, paint  round  the  rivet  heads  with  a  solution  of  soap  and  the 
leak  will  be  found  wherever  a  bubble  or  suds  appear.  To  ascer- 
tain the  number  of  gallons  in  cylinders  and  round  tanks,  multi- 


HANDBOOK    ON    ENiSIXKKUING. 


787 


ply  the  square  of  the  diameter  in  inches  by  the  height  in  inches 
ply  the  square  of  the  diameter  in  inches  by  the  height  in  inches 
and  the  product  by  . 0034  =  gallons.  Weight  of  round  wrought 
iron :  Multiply  the  diameter  by  4,  square  the  product  and  divide 
by  6—: the  weight  in  pounds  per  foot.  To  find  the  weight  of  a 
casting  from  the  weight  of  a  pine  pattern,  multiply  one  pound  of 
pattern  by  16.7,  for  cast-iron,  and  by  19  for  brass.  Ordinary 
gray  iron  castings  =  about  4  cubic  inches  to  the  pound. 

Water* —  A  gallon  of  water  (U.  S.  Standard)  contains  231 
cu.  in.  and  weighs  8^  Ibs.  A  cubic  foot  of  water  contains  7£  gal- 
or  1728  cu.  in.  and  weighs  62.425  Ibs.  A  t;  Miner's  inch"  is  a 
measure  for  the  flow  of  water  and  is  the  amount  discharged 
through  an  opening  1  inch  square  in  a  plank  2  in.  in  thickness, 
under  a  head  of  6  in.  to  the  upper  edge  of  the  opening ;  and  this 
is  equal  to  11.625  U.  S.  gal.  per  minute.  The  height  of  a 
column  of  fresh  water,  equal  to  a  pressure  of  1  Ib.  per  sq.  in.,  is 
2.304  feet.  A  column  of  water  1  ft.  high  exerts  a  pressure  of  .433 
Ibs.  per  sq.  in.  The  capacity  of  a  cylinder  in  gallons  is  equal  to 
the  length  in  inches  multiplied  by  the  area  in  inches,  divided  by 
231  (the  cubical  contents  of  one  U.  S.  gal.  in  inches).  The 
velocity  in  feet  per  minute,  necessary  to  discharge  a  given  volume 
of  water  in  a  given  time,  is  found  by  multiplying  the  number  of 
cu.  ft.  of  water  by  144  and  dividing  the  product  by  the  area  of 
the  pipe  in  inches. 

Decimal  Equivalents  of  an  Inch. 


1*16 

1-8 

3-16 

1-4 

5-16 

3-8     7-16 

1-2 

.0025 

.125 

.1875 

.25 

.3126 

.375  !  .4375 

.5 

9-16 

5-8 

11-16 

3-4 

13-16 

7-8    15-16 

.5625 

.625 

.6875 

.75 

.8125 

.875  1   -9375 

788  HANDBOOK    ON    ENGINEERING. 


CHAPTER     XXVII. 

THE  DRIVING  POWER  OF  BELTS. 

The  average  strain  or  tension  at  which  belting  should  be  run, 
is  claimed  to  be  55  pounds  for  every  inch  in  width  of  a  single  belt, 
and  the  estimated  grip  is  one-half  pound  for  every  square  inch  of 
contact  with  pulley,  when  touching  one-half  of  the  circumference 
of  the  pulley.  For  instance  a  belt  running  around  a  36-inch  pul- 
ley would  come  in  contact  with  one-half  its  circumference,  or  56J 
inches,  and  allowing. a  half-pound  per  inch,  would  have  a  grip  28J 
pounds  for  each  inch  of  width  of  belt. 

nECHANICAL  PROBLEMS  AND  RULES. 

Problem  1.  To  find  the  circumference  of  a  circle  or  a 
pulley :  — 

Solution.  Multiply  the  diameter  by  3.1416  ;  or,  as  7  is  to  22 
so  is  the  diameter  to  the  circumference. 

Problem  2.     To  compute  the  diameter  of  a  circle  or  pulley:  — 

Solution.  Divide  the  circumference  by  3.1416;  or  multiply 
the  circumference  by  .3183  ;  or  as  22  is  to  7,  so  is  the  circumfer- 
ence to  the  diameter,  equally  applicable  to  a  train  of  pulleys,  the 
given  elements  being  the  diameter  and  the  circumference. 

Problem  3.  To  find  the  number  of  revolutions  of  driven  pulley, 
the  revolution  of  driver,  and  diameter  of  driver  and  driven  being 
given :  — 

Solution.  Multiply  the  revolutions  of  driver  by  its  diameter, 
and  divide  the  product  by  the  diameter  of  driven. 


HANDBOOK    ON   ENGINEERING.  789 

Problem  4.  To  compute  the  diameter  of  driven  pulley  for  any 
desired  number  of  revolutions,  the  size  and  velocity  of  driver 
being  known :  — 

Solution.  Multiply  the  velocity  of  driver  by  its  diameter  and 
divide  the  product  by  the  number  of  revolutions  it  is  desired  the 
driven  shall  make. 

Problem  5.     To  ascertain  diameter  of  driving  pulley :  — 

Solution.  Multiply  the  diameter  of  driven  by  the  number  of 
revolutions  you  desire  it  shall  make,  and  divide  the  product  by 
the  number  of  revolutions  of  the  driver. 

0.  Rule  for  finding  length  of  belt  wanted:  Add  the  diame- 
ters of  the  two.  pulleys  together,  divide  the  result  by  two,  and 
multiply  the  quotient  by  3  1/7.  Add  the  product  to  twice  the 
distance  between  the  centers  of  the  shafts,  and  you  have  the 
length  required. 

FOR  CALCULATING  THE  NUMBER  OF  HORSE-POWER  WHICH  A  BELT 
WILL  TRANSMIT,  ITS  VELOCITY  AND  THE  NUMBER  OF  SQUARE  INCHES 
IN  CONTACT  WITH  THE  PULLEY  BEING  KNOWN. 

Divide  the  number  of  square  inches  of  belt  in  contact  with  the 
pulley  by  two,  multiply  this  quotient  by  velocity  of  the  belt  in 
feet  per  minute  and  divide  the  product  by  33,000  ;  the  quotient  is 
the  number  of  horse-power. 

Example.  —  A  20-inch  belt  is  being  moved  with  a  velocity  of 
2,000  feet  per  minute,  with  six  feet  of  its  length  in  contact 
with  the  circumference  of  a  four-foot  drum ;  desired  its  horse- 
power. 20  x  72  equal  1,440,  divided  by  two,  equals  720  x  2,000 
equal  1,440,000  divided  by  33,000  equal  43|  horse-power. 

Rule  for  finding  width  of  belt,  when  speed  of  belt  in  feet  per 
minute  and  horse  power  wanted  are  given :  — 

For  single  belts,  —  Divide  the  speed  of  belt  by  800.  The  horse- 
power wanted  divided  by  this  quotient,  witt/give'the  width  of 
belt  required. 


790  HANDBOOK    ON    ENGINEERING. 

Example.  — Required  the  width  of  single  belt  to  transmit  100 
horse-power.  P^ngine  pulley  72"  in  diameter.  Speed  of  engine, 
220  revolutions  per  minute. 

800)  4146  (speed  of  belt  per  minute). 

5,18)100.00  (horse-power  wanted). 
19"  width  of  belt  required. 

For  double  belts*  —  Divide  the  speed  of  belt  in  feet  per  minute 
by  560.  Divide  the  horse-power  wanted  by  this  quotient  for  the 
width  of  belt  required. 

Example.  —  Required  the  width  of  double  belt  to  transmit  500 
horse-power.  Engine  pulley  72"  in  diameter.  Speed  of  engine, 
220  revolutions  per  minute. 

560)4146  (speed  of  belt  per  minute). 
7.4)500.00  (horse-power  wanted). 
67|"  width  of  belt  required. 


EXTRACTS  FROM  ARTICLES  ON  BELTS. 

BY    II.  .T.   ABERNATHEY. 

Although  there  is  not  near  as  much  known  in  general  about 
the  power  of  transmitting  agencies  as  there  should  be,  still  it 
seems  that  almost  any  other  method  or  means  is  better  understood 
than  belts. 

One  of  the  chief  difficulties  in  the  way  of  a  better  knowledge  of 
the  belting  problem,  is  the  relation  that  belts  and  pulleys  bear  to 
each  other.  The  general  supposition,  and  one  that  leads  to  many 
errors,  is  that  the  larger  in  diameter  a  pulley  is,  the  greater  its 
holding  capacity  —  the  belt  will  not  slip  so  easily,  is  the  belief. 
But  it  is  merely  a  belief,  and  has  nothing  to  sustain  it,  unless  it 
be  faith,  and  faith  without  work  is  an  uncertain  factor.  I  would 


HANDBOOK    ON    ENGINEERING.  791 

like  here  to  impress  upon  the  minds  of  all  interested,  the  following 
immutable  principles  or  law  :  — 

1.  The  adhesion  of  the  belt  to  the  pulley  is  the  same  —  the  arc 
or   number   of  degrees   of  contact,  aggregate  tension  or  weight 
being  the  same  —  without  reference  to  width  of  belt  or  diameter 
of  pulley. 

2.  A  belt  will  slip  just  as  readily  on  a  pulley  four  feet  in  diam- 
eter, as  it  will  o'n  a  pulley   two  feet  in   diameter,    provided  the 
conditions  of  the  faces  of  the  pulleys,  the  arc  of  contact,  the  ten- 
sion, and  the  number  of  feet  the  belt  travels  per  minute  are  the 
same  in  both  cases. 

3.  A  belt  of  a  given  width  and  making  two  thousand,  or   any 
other  given  number  of  feet  per  minute,  will  transmit  as  much 
power    running   on    pulleys    two    feet   in  diameter    as  it  will  on 
pulleys  four  feet  in  diameter,  provided  the  arc  of  contact,  tension 
and  conditions  of  pulley  faces  all  be  the  same  in  both  cases. 

It  must  be  remembered,  in  reference  to  the  first  rule,  that  when 
speaking  of  tensions,  that  aggregate  tension  is  never  meant  unless 
so  specified.  A  belt  six  inches  wide,  with  the  same  tension,  or 
as  taut  as  a  belt  one  inch  wide,  would  have  six  times  the  aggre- 
gate tension  of  the  one  inch  belt.  Or  it  would  take  six  times 
the  force  to  slip  the  six  inch  belt  as  it  would  the  one  inch.  I 
prefer  to  make  the  readers  of  this,  practical  students.  I  want 
them  to  learn  for  themselves.  Information  obtained  in  that  way 
is  far  more  valuable,  and  liable  to  last  much  longer. 

In  order  that  the  reader  may  more  fully  understand  whether 
or  not  a  large  pulley  will  hold  better  than  a  small  one,  let  him 
provide  a  short,  stout  shaft,  say  three  or  four  feet  long  and  two 
inches  in  diameter.  To  this  shaft  firmly  fasten  a  pulley,  say 
12  in.  in  diameter,  or  any  other  size  small  pulley"  that  may  be 
convenient.  The  shaft  must  then  be  raised  a  few  feet  from  the 
floor  and  firmly  fastened,  either  in  vices,  or  by  some  other  means, 
so  that  it  will  not  turn.  It  would  IK-  better,  of  course,  to  have 


D'E  L'., 

OF  THE  J\ 


792  HANDBOOK    ON    ENGINEERING. 

a  suiooth-faced  iron  pulley,  as  such  are  most  generally  used.  So 
far  as  the  experiment  is  concerned,  it  would  make  no  difference 
what  kind  of  a  pulley  was  used,  provided  all  the  pulleys  experi- 
mented with  be  of  the  same  kind,  and  have  the  same  kind  of  face 
finish.  When  the  shaft  and  pulleys  are  fixed  in  place,  procure  a 
new  leather  belt  and  throw  it  over  the  pulley.  To  one  end  of  the 
belt  attach  a  weight,  equal,  say,  to  forty  pounds  —  or  heavier,  if 
desired  —  for  each  inch  in  width  of  belt  used ;  let  the  weight 
rest  on  the  floor.  To  the  other  end  of  the  belt  attach  another 
weight,  and  keep  adding  to  it  until  the  belt  slips  and  raises  the 
first  weight  from  the  floor.  After  the  experimenter  is  satisfied 
with  plaxing  with  the  12  in.  pulley,  he  can  take  it  off  the 
shaft  and  put  on  a  24  in.,  a  3.6  in.,  or  any  other  size  he  may 
wish ;  or,  what  is  better,  he  can  have  all  on  the  shaft  at  the 
same  time.  The  belt  can  then  be  thrown  over  the  large  pulley 
and  the  experiment  repeated.  It  will  then  be  found  if  pulley 
faces  are  alike,  that  the  weight  which  slipped  the  belt  on  the 
small  pulley  will  also  slip  it  on  the  large  one.  The  method 
shows  the  adhesion  of  a  belt  with  180  degrees  contact,  but  as  the 
contact  varies  greatly  in  practice,  it  is  well  enough  to  understand 
what  may  be  accomplished  with  other  arcs  of  contact.  But,  after 
all,  many  are  probably  at  a  loss  how  to  account  for  some  obser- 
vations previously  made.  They  have  noticed  that  when  a  belt  at 
actual  work  slipped,  an  increase  in  the  size  (diameter)  of  the 
pulleys  remedied  the  difficulty  and  prevented  the  slipping. 

A  belt  has  been  known  to  refuse  to  do  the  work  allotted  to  it, 
and  continue  to  slip  over  pulleys  two  feet  in  diameter,  but  from, 
the  moment  pulleys  were  changed  to  three  feet  in  diameter  there 
was  no  further  trouble.  These  observed  facts  seem  to  be  at 
variance  with  and  to  contradict  the  results  of  the  experiments 
that  have  been  made.  All,  however,  may  rest  assured  that  it  is 
only  apparent,  not  real. 

The  resistance  to  slippage  is  simply  a  unit  of  useful  effect  (or 


HANDBOOK    ON    ENGINEERING.  793 

that  which  can  be  converted  into  useful  effect).  The  magnitude 
of  the  unit  is  in  proportion  to  the  tension  of  the  belt.  The  sum 
total  of  useful  effect  depends  upon  the  number  of  times  the  unit, 
is  multiplied.  A  belt  6  inches  wide  and  having  a  tension  equal 
to  40  Ibs.  per  inch  in  width,  and  traveling  at  the  rate  of  1  foot 
per  minute,  will  raise  a  weight  of  240  Ibs.  1  foot  high  per  minute. 
If  the  speed  of  the  belt  be  increased  to  136.5  feet  per  minute,  it 
will  raise  a  weight  of  33,000  Ibs.  per  minute,  or  be  transmitting 
1  horse-power.  The  unit  of  power  transmitted  by  a  belt  is  rather 
more  than  its  tension,  but  to  take  it  at  its  measured  tension  is  at 
all  times  safe,  and  40  to  45  Ibs.  of  a  continuous  working  strain  is 
as  much,  perhaps,  as  a  single  belt  should  be  subjected  to.  A 
little  reflection  will  now  convince  the  reader  that  a  belt  transmits 
power  in  proportion  to  its  lineal  speed,  without  reference  to  the 
diameter  of  the  pulleys.  Having  arrived  at  that  conclusion,  it  is 
then  easy  to  understand  why  it  is  that  a  belt  working  over  36-inch 
pulley  will  do  its  work  easy,  when  it  refused  to  do  it  and  slipped 
on  24-inch  pulleys.  If  the  belt  traveled  800  feet  per  minute  on 
the  24-inch  pulleys,  on  the  36-inch  it  would  travel  1,200  feet, 
thus  giving  it  one-half  more  transmitting  power.  If,  in  the  first 
instance,  it  was  able  to  transmit  but  8  horse-power,  in  the  second 
instance  it  will  transmit  12  horse-power.  All  of  which  is  due  to 
the  increase  in  the  speed  of  the  belt  and  not  to  the  increase  in  the 
size  of  the  pulleys ;  because,  as  has  been  shown,  the  co-efficient 
of  friction,  or  resistance  to  slippage,  is  the  same  on  all  pulleys 
with  the  same  arc  of  belt  contact. 

There  is  no  occasion  for  elaborate  and  perplexing  formulas  and 
intricate  rules.  They  serve  no  useful  purpose,  but  tend  only  to 
mystify  and  puzzle  the  brain  of  all  who  are  not  familiar  with  the 
higher  branches  of  mathematics,  —  and  it  is  the  fewest  number 
of  our  every-day  practical  mechanics  who  are  so  familiar.  In  all, 
or  nearly  all  treatises  on  belting,  the  writer  will  tell  you  that  at 
600,  800  or  1,000  feet  per  minute,  as  the  case  may  be,  a  belt  one 


794  HANDBOOK    ON    ENGINEERING. 

inch  wide,  will  transmit  one  horse-power ;  and  yet,  when  we  come 
to  apply  their  rules  in  practice,  no  such  results  can  be  obtained 
one  time  in  ten.  The  rules  are  just  as  liable  to  make  the  belt 
travel  400,  1,000  or  1,600  per  minute  per  horse-power  as  the' 
number  ,of  feet  they  may  give  as  indicating  a  horse-power. 

I  have  adopted,  and  all  my  calculations  are  based  upon  the 
assumption  that  a  belt  traveling  800  feet  per  minute,  and  running 
over  pulleys,  both  of  which  are  the  same  diameters,  will  easily 
transmit  one  horse-power  for  each  inch  in  width  of  belt.  A  belt 
under  such  circumstances  would  have  180  degrees  of  contact  on 
both  pulleys  without  the  interposition  of  idlers  or  tighteners. 

The  last  proposition  being  accepted  as  true  and  the  basis  cor- 
rect, the  whole  matter  resolves  itself  into  a  very  simple  problem, 
so  far  as  a  belt  with  180  degrees  contact  is  concerned.  It  is 
simply  this :  If  a  belt  traveling  800  feet  per  minute  transmit  one 
horse-power,  at  1,600  feet,  it  will  transmit  two  horse-power ;  or 
if  2,400  feet,  three  horse-power,  and  so  on.  It  is  no  trouble  for 
any  one  to  understand  that,  if  he  understands  simple  multiplica- 
tion or  division. 

It  is  not,  however,  always  the  case  that  both  pulleys  are  the 
same  size,  and  as  soon  as  the  relative  sizes  of  the  pulleys  change, 
the  transmitting  power  of  the  belt  changes ;  and  that  is  the  rea- 
son why  no  general  rule  has  ever,  or  ever  will  be  made  for  ascer- 
taining the  transmitting  capacity  of  belts  under  all  circumstances. 
When  the  pulleys  differ  in  size,  the  larger  of  the  two  is  lost  sight 
of  —  it  no  longer  figures  in  the  calculations  —  the  small  pulley, 
only,  must  be  considered.  To  get  at  it,  the  number  of  degrees 
of  belt  contact  on  the  small  pulley  must  be  ascertained  as  nearly 
as  possible  and  use  for  a  guide,  for  getting  at  the  transmitting 
power,  the  next  established  basis  below.  Of  course,  the  experi- 
menter can  make  a  rule  for  every  degree  of  variation,  but  it  would 
require  a  great  many,  and  is  not  necessary.  I  use  five  divisions, 
as  follows :  — 


HANDBOOK    ON    ENGINEERING.  795 

For   180  degrees    useful    effect     ....      100 

For   157.1,       "  92 

For   135  84 

For   112.i       "  y(J 

For  1)0  "         ....      .<;  1 

The  experimenters  may  find  that  my  figures  are  under  obtained 
results,  which  is  exactly  what  they  are  intended  to  be,  more 
especially  at  the  90  degree  basis.  I  wish  to  make  ample  allow- 
ance. 

To  ascertain  the  power  a  belt  will  transmit  under  the  first-named 
conditions :  Divide  the  speed  of  the  belt  in  feet  per  minute  by 
800,  multiply  by  its  width  in  inches  and  by  100.  For  the  second, 
divide  by  800,  multiply  by  width  in  inches  and  by  .92.  Third 
place,  divide  by  800,  multiply  by  width  in  inches  and  by  .84. 
Fourth  place,  divide  by  800,  multiply  by  width  in  inches  and  by 
.76.  Fifth  place,  divide  by  800,  multiply  by  width  in  inches  and 
by  .64.  As  an  example:  What  would  be  the  transmitting  power 
of  a  16-inch  belt  traveling  2,500  feet  per  minute  by  each  of  the 
above  rules  ? 

1st:    2,500  divided  by  800  equal  3.125x  16  &  100  equal  50  h.  p. 
2d:    2,500  800     "      3.125 x  16  &   .92  equal  46     " 

3d:    2,500  800     "      3.125 x  16  &   .84  equal  42     " 

4th:  2,500  800     "       3.125  x  16  &   .76  equal  38     " 

5th:  2,500  800     "       3. 125  x  16  &   .64  equal  32     " 

As  I  have  said,  if  the  degrees  of  contact  come  between  the 
divisions  named  above,  in  order  to  be  on  the  safe  side,  calculate 
from  the  first  rule  below  it,  or  make  an  approximate  as  you  like. 

If  the  above  lesson  is  studied  well  and  strictly  used,  there  can 
be  no  excuse  for  any  mechanic  putting  in  a  belt  too  small  for  the 
work  it  has  to  do,  provided  he  knows  how  much  there  is  to  do, 
which  he  ought,  somewhere  near  at  least. 


796 


HANDBOOK    ON    ENGINEERING. 


HORSE-POWER  TRANSMITTED   BY  LEATHER 
BELTS. 

DRIVING    POWER    OF    SINGLE    BELTS. 


Speed  in 
Feet  per 

Width  of   Belt  in  Inches. 

Minute. 

2 

3 

4 

5 

6 

8 

10 

12 

14 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.  P. 

H.   P. 

H.  P. 

H.  P. 

H.  P. 

400 

1 

H 

2 

2& 

3 

4 

5 

6 

7 

600 

1J 

2! 

3 

sl 

42 

6 

7* 

9 

101 

800 

2 

3            4 

5 

6 

8 

10 

12 

14 

1,000 

H 

3!          5 

6i 

7* 

10 

121 

15 

17i 

1,200 

3 

H          7 

9 

12 

15 

18 

21 

1,500 
1,800 

31 
4* 

5| 

6| 

2 

9I 
114 

lit 

15 

18 

18| 

221 

222L 
27 

.261 
311 

2,000 

5 

H 

10 

in 

15 

20 

25 

30 

35 

2,400 

6 

9 

12 

15 

18 

24 

30 

36 

42 

2,800 
3,000 

7 

H 

10* 

111 

14 
15. 

17i   j     21 
18|        221 

28 
30 

35 
87* 

42 
45 

49 

521 

3,500 

8| 

13 

17* 

22 

26 

35 

44 

521 

61 

4,000 

10 

15 

20 

25 

30 

40 

50 

60 

70 

4,500 

ill 

17 

22£ 

28 

34 

45 

57 

69 

78 

5,000 

IS 

19 

25 

31 

37£ 

50 

621 

75 

87 

DRIVING   POWER   OF   DOUBLE    BELTS. 


Speed  in 


Width  of  Belts  in  Inches. 


Feet  per 
Minute. 

6  * 

8 

10     12 

14 

16 

18 

20 

24 

H.  P. 

H.  P. 

H.  P.  |  H.  P 

H.  P. 

H.  P. 

fl.  P. 

H.  P 

H.  P. 

400 

44 

5| 

74    8* 

10 

H4 

13 

H4 

174 

600 

6* 

81 

11    13 

15 

174 

194 

22 

26 

800 

4 

111 

14*    174 

20£ 

23 

26 

29 

344 

1,000 

11 

\±\ 

184  !  214 

25i 

29 

324 

36 

434 

1,200 

13 

"I 

22    26 

30i 

344 

39 

44 

524 

1,500 

164 

21| 

274  j  32^ 

38 

434 

49 

544 

654 

1,800 

191 

26 

32|  j  39 

454 

52 

59 

654 

784 

2,000 

21| 

29 

361  |  434 

504 

58 

654 

724 

87 

2,400 

26 

34| 

44    52^ 

604 

694 

784 

88 

105 

2.800 

30| 

40L 

51     61 

71 

81 

914 

102 

122 

3,000 

32  \ 

43i 

54i  I  65^ 

76 

874 

98 

108 

131 

3,500 

38 

50} 

63£  \  76 

89 

101 

114 

127 

153 

4,000 

43i 

68| 

72|  !  87 

101 

116 

131 

145 

174 

4,500 

49 

65 

82    98 

114 

131 

147 

163 

196 

5,000 

541 

72| 

91   i  109  |  127 

145 

163 

182 

218 

HANDBOOK    ON    ENGINEERING.  797 

Example.  —  Required  the  width  of  a  single  belt,  the  velocity  of 
which  is  to  be  1,500  feet  per  minute  ;  it  has  to  transmit  10  horse- 
power, the  diameter  of  the  smaller  drum  being  four  feet  with  five 
feet  of  its  circumference  in  contact  with  the  belt. 

33,000  x  10  equal  330,000,  divided  by  1,500  equal  220,  divided 
by  5  equal  44,  divided  by  6  equal  1\  inches,  the  required  width  of 
belt. 

Directions  for  calculating  the  number  of  horse  power  which  a 
belt  will  transmit.  Divide  the  number  of  square  inches  of  belt  in 
contact  with  the  pulley  by  two ;  multiply  this  quotient  by  the 
velocity  of  the  belt  in  feet  per  minute ;  again  we  divide  the  total 
by  33,000  and  the  quotient  is  the  mumber  of  horse-power. 

Explanations. — The  early  division  by  two  is  to  obtain  the 
number  of  pounds  raised  one  foot  high  per  minute,  half  a  pound 
being  allowed  to  each  square  inch  of  belting  in  contact  with  the 
pulley. 

Example.  —  A  six-inch  single  belt  is  being  moved  with  a 
velocity  of  1,200  feet  per  minute,  with  four  feet  of  its  length  in 
contact ^with  a  three-foot  drum.  Required  the  horse-power. 

6x48  equal  288,  divided  by  2  equal  144  x  1,200  equal  172,- 
800,  divided  by  33,000  equal,  say,  5J  horse-power. 

It  is  safe  to  reckon  that  a  double  belt  will  do  half  as  much 
work  again  as  a  single  one. 

Hints  to  users  of  belts.  —  1.  Horizontal,  inclined  and  long 
belts  give  a  much  better  effect  than  vertical  and  short  belts. 

2.  Short  belts   require,  to   be  tighter  than  long  ones.     A  long 
belt  working  horizontally  increases  the  grip  by  its  own  weight. 

3.  If  there   is  too  great  a  distance  between  the  pulleys,  the 
weight  of  the  belt  will  produce  a  heavy  sag,  drawing  so  hard  on 
the  shaft  as  to  cause  great  friction  at  the  bearings  ;  while,  at  the 
same  time,  the   belt  will  have  an  unsteady  motion,  injurious  to 
itself  and  to  the  machinery. 

4.  Care  should  be  taken  to  let  the  belts  run  free  and  easy,  so 


HANDBOOK    ON    ENGINEERING^. 

as  to  prevent  the  tearing  out  of  the  lace  holes  at  the  lap  ;  it  also 
prevents  the  rapid  wear  of  the  metal  bearings. 

5.  It  is  asserted  that  the  grain  side  of  a  belt  put  next  to  the 
pulley  will  drive  30  per  cent  more  than  the  flesh  side. 

6.  To  obtain  a  greater  amount  of  power  from  the  belts  the  pul- 
leys may  be  covered  with  leather ;  this  will  allow  the  belts  to  run 
very  slack  and  give  25  per  cent  more  durability. 

7.  Leather  belts  should  be  well  protected  against  water  and  even 
loose  steam  and  other  moisture. 

-8.  In  putting  on  a  belt,  be  sure  that  the  joints  run  with  the 
pulleys,  and  not  against  them  out. 

9.  In  punching  a  belt  for  lacing,  it  is  desirable  to  use  an  oval 
punch,  the  larger  diameter  of  the  punch  being  parallel  with  the 
belt,  so  as  to  cut  out  as  little  of  the  effective  section  of  the  leather 
as  possible. 

10.  Begin  to  lace  in  the  center  of  the  belt  and  take  care  to  keep 
the  ends  exactly  in  line  and  to  lace  both  sides  with  equal  tight- 
ness.   The  lacing  should  not  be  crossed  on  the  side  of  the  belt  that 
runs  next  the  pulley.    Thin  but  strong  laces  only  should  be  used. 

11.  It  is  desirable  to  locate  the  shafting  and  machinery  so  that 
belts  shall  run  off  from  each  other  in  opposite  directions,  as  this 
arrangement  will  relieve  the  bearings  from  the  friction  that  would 
result  where  the  belts  all  pull  one  way  on  the  shaft. 

12.  If  possible,  the  machinery  should  be   so  planned  that  the 
direction  of  the  belt  motion  shall  be  from  the  top  of  the  driving  to 
the  top  of  the  driven  pulley. 

18.  Never  overload  a  belt. 

14.  A  careful  attention  will  make  a  belt  last  many  years,  which 
through  neglect  might  not  last  one. 

DIRECTIONS  FOR  ADJUSTING  BELTING. 

In    lacing  cut   the    ends   perfectly  square,  else   the  belt  will 
stretch  unevenly.     Make  two  rows  of  holes  in  each  end  ;  put  the 


HANDBOOK    ON     F.XC  I  N  .-IKKI  N  < ',  . 


ends  together    and  lace  with  lace  leather,  as  shewn  in  the  cuts 
below.     For  wide  belts,  in  addition,  put  a  thin  piece  of  leather  or 


I 


rubber  on  the  back  to  strengthen  the  joint,  equal  in  length  to  the 
width  of  the  belt,  and  sew  or  rivet  it  to  the  belt.  In  putting  on 
belting,  it  should  be  stretched  as  tight  as  possible,  and  with  wide 
belts,  this  can  be  done  best  by  the  use  of  belt  clamps. 


HORSE  POWER  OF  BELTING. 

To  ascertain  horse-power  which  belts  will  transmit,  multiply 
width  of  belt  by  diameter  of  pulley  (in  inches),  by  revolutions 
of  pulley  (per  minute),  by  number  in  table  (corresponding  to  the 
pull  the  belt  can  exert  per  inch  of  width). 

Example. —  10"  single  horizontal  belt,  36"  pulley,  200  revolu- 
tions, pull  taken  at  50  Ibs. 

10"  x  36"  x  200  x  0.0004  =  28.8  horse-power. 

The  pulls  which  belts  1"  wide  will  transmit  are  as  follows :  — 
Single  horizontal  belts    (pulleys   nearly  same  diameter)    50  Ibs. 
Double       "  100 

Single  vertical         "  40 

Double       "  "  "  60 

Single  belts  (large  to  very  small  pulleys)       ....        10 
Double    "  "  "  ....        15 

Quarter  twist,  single  belts 25 

"          **       double    "  ...       40 


HANDBOOK    ON    ENGINEERING . 


CHAPTER     XXVIII. 
[CAPACITY  OF  AIR  COHPRESSORS. 

To  ascertain  the  capacity  of  an  air  compressor  in  cubic  feet  of 
free  air  per  minute,  the  common  practice  is  to  multiply  the  area 
of  the  intake  cylinder  by  the  feet  of  piston  travel  per  minute. 
The  free  air  capacity  of  the  compressor,  divided  by  the  number 
of  atmospheres,  will  give  the  volume  of  compressed  air  per 
minute.  To  ascertain  the  number  of  atmospheres  at  any  given 
pressure,  add  15  Ibs.  to  the  gauge  pressure ;  divide  this  sum  by 
15  and  the  result  will  be  the  number  of  atmospheres.  The  above 
method  of  calculation,  however,  is  only  theoretical  and  these 
results  are  never  obtained  in  actual  practice,  even  with  com- 
pressors of  the  very  best  design  working  under  the  most  favor- 
able conditions  obtainable.  Allowances  should  be  made  for 
losses  of  various  kinds,'  the  principal  losses  being  due  to  clear- 
ance spaces,  but  in  machines  of  poor  design  and  construction 
other  losses  occur  through  imperfect  cooling,  leakages  past  the 
piston  and  through  the  discharge  valves,  insufficient  area  and 
improper  working  of  inlet  valves,  etc.  The  writer  has  seen  com- 
pressors where  losses  through  imperfections  and  improper  working 
conditions  ranged  from  15  to  25  per  cent,  while  under  favorable 
conditions  and  with  the  average  compressor,  the  loss  averages 
from  8  to  12  per  cent.  So  that  to  get  sufficiently  accurate 
results  in  finding  capacity  of  the  compressor,  "subtract  12  per 
cent  from  above  computation,  which  gives  nearly  accurate 
figures.  The  following  table  will  be  found  useful  for  quickly 
ascertaining  the  capacity  of  an  air  compressor,  also  to  find  the 
cubical  contents  of  any  cylinder,  receiver,  etc.  The  first  column 


HANDBOOK    ON    ENGINEERING. 


801 


is  the  diam.  of  cylinder  in  inches.     The  second  shows  the  cubical 
contents  in  feet,  for  each  foot  in  length. 

Contents  of  a  Cylinder  in  Cubic  Feet  for  Each  Foot 

in  Length. 


a  g 

M 

QJ2 

Cubic 
Contents. 

l's 

rt  J3 

5§ 

Cubic 
Contents. 

P 

«5 

Cubic 
Contents. 

aS 

5*8 

«S 

Cubic 
Contents. 

Diam. 
Inches. 

Cubic 
Contents. 

i 

.0055 

6 

.1963 

11 

.6600 

20 

2.182 

36 

7.069 

U 

.0085 

64 

.2130 

H4 

.6903 

204 

2.292 

37 

7.468 

ii 

.0123 

64 

.2305 

H4 

.7213 

21 

2.405 

38 

7.886 

II 

.0168 

SI 

.2485 

HI 

.7530 

214 

2.521 

39 

8.296 

2 

.0218 

7 

.2673 

12 

.7854 

22 

2.640 

40 

8.728 

24 

.0276 

M 

.2868 

124 

.8523 

224 

2.761 

41 

9.168 

*i 

.0341 

74 

.3068 

13 

.9218 

23 

2.885 

42 

9.620 

21 

.0413 

71 

.3275 

134 

.9940 

234 

2.885 

43 

10.084 

3 

.0401 

8 

.3490 

14 

1.069 

24 

3.012 

44 

10.560 

34 

.0576 

84 

.3713 

144 

1.147 

25 

3.142 

45 

11.044 

34 

.0668 

84 

.3940 

15 

1.227 

26 

3.400 

46 

11.540 

31 

.07H7 

81 

.4175 

154 

1.310 

27 

3.687 

47 

12.048 

4 

.0873 

9 

.4418 

16 

1.396 

28 

3.976 

48 

12.566 

4* 

.0985 

94 

.4668 

164 

1.485 

29 

4.587 



44 

.1105 

94 

.4923 

17 

1.576 

30 

4.909 

.  . 

...... 

41 

.1231 

91 

.5185 

174 

1.670 

31 

5.241 



5 

.1364 

10 

.5455 

18 

1.767 

32 

5.585 

64 

.1503 

104 

.5730 

184 

1.867 

33 

5.940 

.. 



54 

.1650 

104 

.6013 

19 

1.969 

34 

6.305 



5£ 

.1803 

101 

.6303 

194 

2.074 

35 

6.681 

To  find  the  capacity  of  an  air-cylinder,  multiply  the  figures  in 
the  second  column  by  the  piston  travel  in  feet  per  minute.  This 
applies  to  double-acting  air  cylinders.  In  the  case  of  single- 
acting  air  cylinders,  the  result  should  be  divided  by  2. 

THE  McKIERMAN  DRILL  COMPANY'S  AIR  COHPRESSOR. 

The  air-cylinder  and  water-jacket  are  one  complete  casting. 
The  heads  are  made  with  hoods  and  provision  made  for  cool  air 

in- take. 

51 


802  HANDBOOK    ON    ENGINEERING. 

The  atmosphere  valves  are  bronze,  of  poppet  form.  There- 
fore, there  is  no  vacuum  and  the  cylinder  fills  absolutely  with  free 
air.  The  valves  are  closed  by  mechanical  means. 

The  discharge  valves  are  self-acting,  are  made  of  bronze.  All 
of  them  are  free  to  inspection  without  removal  or  disturbance  of 
other  parts. 

The  cooling  apparatus,  or  heat-preventing  device,  is  extremely 
effective.  Water  jacket  completely  surrounds  the  cylinder,  water 


is  forced  to  wash  the  walls  and  is  kept  in  rapid  motion  from  bot- 
tom to  top,  from  end  to  end,  absorbing  heat  rapidly.  It  enters 
the  jacket  at  bottom,  flows  from  end  to  end,  around  partitions, 
back  and  forth  and  up.  Follows  natural  laws  in  absorbing, 
retaining  and  dispelling  the  heat  of  air. 

Regulation  of  pressure  and  speed  is  entirely  automatic.  The 
regulating  device  is  the  only  one  by  which  the  air  weighs  the 
steam  admitted  to  the  cylinder.  Throttle  may  be  thrown  wide 
open  at  start,  then  the  regulator  takes  absolute  control,  governing 
the  speed  from  highest  to  lowest  rate,  varying  the  speed  for 


HANDBOOK    ON    ENGINEERING. 


803 


variable  amounts  of  air  which  may  be  required  and  in  such  man- 
ner as  to  keep  the  pressure  constant. 


i  IN  SECTION.  AiK-tja-i*'jt*-  EM'  KIEVATK 

I    Snu»'ir.G  VALVE*. 

The  Bennett  Automatic  Air  Compressor. 


Ingersoll-Sergeant  Air  Compressor, 


804  HANDBOOK    ON    ENGINEERING. 

INGERSOLL-SERGEANT  AIR  COMPRESSOR, 

This  engine,  a  cut  of  which  is  shown  above,  is  fitted  with  In- 
gersoll-Sergeant  Air  Compressor  Cylinders,  and  in  connection 
with  the  Pohle  Air  Lift  System,  has  double  the  supply  of  water, 
using  only  one- half  the  fuel  previously  required.  The  steam 
cylinders  are  of  the  Duplex  Corliss  condensing  type  and  con- 
necting tandem,  and  on  each  side  are  two  Ingersoll-Sergeant  Air 
Cylinders  and  two  Conover  Water  Cylinders.  .When  the  engine 


SECTIONAL    VIEW    OP   AIR    CYLINDER    WITH   VERTICAL  LIFT   VALVES,  USED 
CLAS5  "E"    AND  "F"  COMPRESSORS. 


is  in  operation,  the  air  cylinders  raise  the  water  by  the  Pohle  Air 
Lift  System,  from  the  wells  to  a  tank  at  the  surface,  and  from 
there  it  is  taken  by  the  water  cylinders  and  forced  to  the  stand- 
pipe.  The  cost  of  this  combination  compares  favorably  with  the 
old  plan  of  using  separate  compressors  and  water  pumps,  each 
with  their  own  steam  cylinders,  and  the  saving  in  attendance, 
friction  and  foundation  commends  its  use.  The  engines  run  at  a 
fixed  moderate  speed  and  the  regulation  of  the  air  and  water  is 
effected  by  passing  the  water  from  suction  to  discharge  when  the 
tank  is  too  low  and  by  mechanically  unloading  the  air  cylinders 


HANDBOOK    ON    ENGINEERING.  805 

with  a  pressure  regulator  when  the  tank  is  too  full.  The  regula- 
tion is  cbne  mechanically,  with  floats  at  the  top  and  bottom  of  the 
'•eceiving  tank.  This  combination  can  also  be  furnished  with 
Straight  Line  Compressors ;  the  advantage  of  the  Duplex  is  that 
should  it  be  necessary,  the  one  side  of  the  engine  can  be  discon- 
nected and  the  other  side  made  to  do  the  work. 

As  will  be  seen,  the  inlet  valves  which  are  on  the  lower  side  of 
the  cylinder  are  offset,  thus  preventing  their  being  sucked  into 
the  cylinder  and  wrecking  the  compressor.  They  are  made  out 
ol  a  solid  piece  of  steel  and  are  extremely  durable,  because  they 
are  placed  vertically,  work  in  a  bath  of  oil  and  do  not  slide  on 
their  seats.  Both  the  inlet  and  discharge  valves,  being  in 
the  cylinder,  allow  the  heads  to  be  thoroughly  water- jacketed, 
and  this  is  an  important  feature  when  it  is  remembered  that 
the  heat  of  compression  is  greatest  at  the  end  of  the  stroke. 
The  cylinder  is,  therefore,  completely  water- jacketed.  The 
valves  are  arranged  so  that  the  air  can  be  taken  from  outside  of 
the  engine  room,  which  increases  the  efficiency  of  the  machine  8 
to  15  per  cent,  and  are  easily  accessible. 

The  two  inlet  valves  are  located  in  the  piston,  and,  with 
the  tube,  are  carried  back  and  forth  with  the  piston.  The  valve 
on  that  face  of  the  piston  which  is  toward  the  direction  of  move- 
ment is  closed,  while  the  one  on  the  other  face  is  open.  This  is 
exactly  as  it  should  be  in  order  to  force  out  the  compressed  air 
from  one  end  of  the  cylinder  while  taking  in  the  free  air  at  the 
other ;  when  the  piston  has  reached  the  end  of  its  travel  there  is, 
of  course,  a  complete  stop  while  the  engine  is  passing  the  center, 
and  an  immediate  start  in  the  other  direction.  The  valve  which 
was  open  immediately  closes.  There  is  no  reason  for  its  remain- 
ing open  any  longer,  and  it  closes  at  exactly  the  right  time,  its 
own  weight  being  all  that  is  necessary  to  move  it.  The  valve 
on  the  other  side  is  left  behind  by  the  piston  and  the  free  air 
is  admitted  to  that  end  of  the  cylinder  for  compression  on  the 


806 


HANDBOOK    ON    ENGINEERING. 


return  stroke.  No  springs  are  used,  and  there  is  none  of  the 
throttling  of  the  incoming  air,  and  none  of  the  clattering  or 
hammering  so  noticeable  with  poppet-valves.  As  there  is  nothing 
to  make  the  valve  move  faster  than  the  piston,  it  stays  behind  until 
the  piston  stops,  leaving  the  port  wide  open  for  the  admission 


DETAILS  OF  PISTON   INLET  AIR  CYLINDER. 

A.— Circulating  Water  Inlet.  D.— Oil  Hole  for  Automatic  Oil  Cup.  G.— Piston  Inlet  Valv 
B.— Circulating  Water  Outlet.  'E.— Air  Inlet  (through  piston  inlet? pipe).  H.— Discharge  Valva. 
C. -Water  Jacket  Drain  Pipe.  F.— Air  Discharge  (showi&g  flange)?  J.-Water  Jacket. 

Sectional  Cut  of  Ingersoll  &  Sargeant  Single  Compressor, 


of  air.  It  is  well  known  that  while  the  fly-wheel  and,  of  course 
the  crank,  rotate  at  a  uniform  speed,  the  movement  of  the  pistoi 
is  not  uniform,  but  gradually  increases  in  speed  from  the  star" 
till  the  crank  has  reached  half -stroke,  when  it  gradually  slows  u{ 
till  the  crank  is  on  the  center,  and  at  this  moment  of  full  stoj 
the  valve  gently  slides  to  its  seat. 


HANDBOOK    ON    ENGINEERING. 


The  above  is  what  is  called  the  Pohle  Air  Lift 
System. 


808  HANDBOOK    ON    ENGINEERING. 

The  illustrations  on  page  807  shows  the  method  of  pumping 
water  by  air.  A  compressor  in  connection  with  the  air-lift  sys- 
tem of  pumping  water  by  direct  air  pressure.  The  pump  con- 
sists of  a  water  pipe  and  an  air  pipe,  the  latter  discharging  the 
air  into  the  former  at  its  bottom,  through  a  specially  designed 
foot-piece.  The  natural  levity  of  the  air  compared  with  the 
water,  causes  it  to  rise  and,  in  rising,  to  carry  the  water  with  it 
in  the  form  of  successive  pistons,  following  one  another.  This 
system  of  pumping  has  found  a  large  range  of  application  and  is 
of  peculiar  service  in  connection  with  deep  well  pumping.  For 
this  purpose,  the  absence  of  mechanical  parts  many  feet  below 
the  surface,  offers  a  commanding  advantage.  Method  No.  1  and 
No.  2  is  almost  alike,  consisting  of  placing  the  air  and  water 
pipes  alongside  of  one  another  in  the  well,  connecting  them  at 
the  bottom  with  an  end  piece.  Method  No.  3  consists  of  placing 
a  water  discharge  pipe  into  the  well ;  the  air  passing  down  into 
the  well  through  the  annular  space  between  the  well  casing  and 
the  water  pipe.  Method  No.  4  consists  in  using  the  well  casing 
as  the  water  discharge  pipe,  and  simply  putting  an  air  pipe  down 
into  the  well,  with  a  specially  designed  foot-piece  attached  at  the 
bottom  through  which  the  air  escapes. 


HANDBOOK    ON    ENGINEERING.  809 


CHAPTER    XXVIII.  — CONTINUED. 
THE  METRIC  SYSTEM. 

It  frequently  happens  that  an  engineer,  in  reading  books  and 
papers  devoted  to  steam  engineering,  is  confronted  -with  terms 
taken  from  the  metric  system,  which  he  does  not  understand. 
I  give  below  a  few  of  the  metric  system  terms  most  commonly 
used,  with  their  values  in  feet  and  inches,  also,  gallons,  quarts, 
pounds,  tons,  etc. 

A  French  meter  is  30.37079  inches  long,  or  a  little  less  than 
39f  inches.  It  is  generally  taken,  —  for  convenience  in  fig- 
uring,—  at  39.37  inches. 

1  decimeter  is  -f^  of  a  meter,  or,  3.937  inches  nearly. 

1  centimeter  is  yj^   "          "     "        .3937     "          " 

1  millimeter  is  T^o-  "          "     "        .03937  "          " 

ALSO. 

1  decameter  equals       10  meters,  or,  32.80  feet  nearly. 
1  hectometer     "         100       "        "328       "         " 

1  kilometer        "       1000      "        "     3280     "         " 

.. 

APPLICATION. 

1.  An  engine  shaft  is  5  meters  long,  what  is  its  length  in  feet 
and  inches?  Ans.   16  ft.  4J  ins.  nearly. 

Operation  :  39_L3J  ><_?  =  16.4  ft.  nearly. 

\a 

2.  An   engine  cylinder   is    10.3  decimeters  in  diameter,  how 
much  is  this  in  inches?  Ans.  40J  ins.  nearly. 

Operation:  3.937  X  10.3  =  40.55  ins.  nearly. 


810  HANDBOOK    ON    ENGINEERING. 

3.  A  piston-rod  is  8.7  centimeters  in  diameter,  how  much  is 
this  in  inches  ?  Ans.   3|  ins.  nearly. 

Operation :  .3937  X  8.7  =  3.42  ins.  nearly. 

4.  A  chimney  is  5.1  decameters  tall,  how  much  is  this  in  feet 
and  inches?  Ans.   167  ft.  3  ins.  nearly. 

Operation :  32.80  X  5.1  =  167.28  ft. 

5.  How  many  miles  are  there  in  30.2  kilometers? 

Ans.   18^  miles  nearly. 
Operation :  There  are  5280  ft.  in  a  mile. 

Then,   828°  ><  8Q-2  ^  18.7  miles. 
5280 

6.  A  valve  has  2  millimeters  lead,  how  much  is  this  in  frac- 
tional parts  of  an  inch?  Ans.  ^  in.  nearly. 

Operation:  .03937  X  2  =  .07874. 
And,  .07874  X  6"4  =  /¥  nearly. 

7.  How  many  square  feet  in  a  circle  whose  diameter  is  one 
meter?  Ans.  8*  nearly. 

n  39.37  X  39.37  X  .7854 

Operation :  -  —  =  8.45. 

144 

8.  The  cylinder  clearance  is    1.1  cubic   decimeter,  how   many 
cubic  inches  in  the  clearance?  Ans.  67  nearly. 

Operation:  3.937  X  3.937  X  3.937  X  1.1=67.12+ 

ALSO. 

1  gramme  equals  15.433  grains,  or  1  ounce  nearly. 
1  kilogramme  equals  2.2047  pounds  avoirdupois. 
I  tonne  equals  1.1024  tons  of  2000  Ibs. 

ALSO. 

1  litre  equals  1.0566  quarts. 


HANDBOOK    ON    ENGINEERING.  811 


CONSEQUENTLY. 

1  U.  S.  gallon  equais  3.79  litres  nearly. 
1  U.  S.  pint  equals  .4732  litres  nearly. 

1.  A  main  shaft  weighs  800  kilogrammes,  how  much  is  this  in 
avoirdupois  pounds?  Ans.  1763J  Ibs.  nearly. 

Operation:     2.2047  X  800  =  1763.76. 

2.  An  engine  weighs  12  tonnes,  how  much  is  this  in  U.  S.  tons 
of  2000  Ibs.  each?  Ans..  13J  tons  nearly. 

Operation:  1.1024  X  12  =  13.2288. 

3.  A  tank  contains   9000  litres  of  water,  how  much  is  this  in 
U.  S.  gallons?  Ans.  2377.35  galls. 

1.0566   X  9000 
Operation:      r Because  4  quarts  equal  1  gallon. 


THERMOMETERS. 

In  the  U.  S*  the  Fahrenheit  scale  is  the  one  in  most  common 
use,  although  in  our  laboratories  and  for  scientific  purposes  it  is 
displaced  by  the  Reaumer  and  Centigrade  scales.  Fahrenheit's 
scale  marks  the  boiling  point  by  212  degrees,  and  the  freezing 
point  by  32  degrees  above  zero. 

The  Reaumer  scale  marks  the  boiling  point  by  80  degrees,  and 
the  freezing  point  by  zero. 

The  Centigrade,  or  Celsius  scale,  marks  the  boiling  point  by 
100  degrees,  and  the  freezing  point  by  zero.  So  that,  reckoning 
from  the  freezing  point  of  Fahrenheit,  180  degrees  Fah.  equal 
80  degrees  Reaumer,  and  100  degrees  Centigrade.  Bearing  in 
mind  that  Fahrenheit's  zero  is  32  degrees  below  the  freezing  point, 
one  scale  may  readily  be  converted  into  another. 

To  convert  degs.  of  Reaumer  into  those  of  Fah. 

Rule*  —  Multiply  by  9,  divide  by  4,  and  add  32. 


I/  MA.  <> 

Example!  '•''   <!''#*•  f<<->i<"ti<  (  /<(.IH|  b 

AM*, 
Operation*  MX*      720, 

*'  / 

A».  'i,       IM  (HO.     it  i  ' 

4 


To  00WJft  titt  dtff  /  04  (/V-ntiKrwl*'  into  n>"<'  ».i    i 
Rule,—  Multiply  \iy  ti,  <livi<l«'.  l.y  A,  ;2. 

faillijrff  f  MO  f1<*tfH,  (/VrillgrA'lf  <'|'u.l  how  i 


Operation* 

Aii«l,  -IW), 


So,  nl*o,  ft  d«'K«,  Oftlfgrful*  WJIIA!  H7.2  <1«'^*<    I  M»IM  ni. 
»X^      27,     AinJf     ,     :fl,2.  Thmi, 

ROPH  TRAN»MIHIIION 


There  Are  two  AyM^rrm   of   ro|m  imfinni^^  i 

^yftkw,  wild  Mifl  Amnrlmti  mou^  w 

ro|i«  nyMf^m  In  whl«h  th«  m«<f*iMftfy  ftdhAMlon  of  »  -j 
olihtiiiMl  l»y  H  t^tldotl <NUttifti      I  will  tr««»l,  of  ll,.    A  ^<y»- 

ofily,  fm  It  l«  ftlrnont  QolfifVttlly  uw<1  in  ililn  fo»i,i 

-    of    MM     ot!«T.       OflA  Of  illH  fflOMi  IMlflMir  •'  •    •   '  •   '  •• 

1    MM     i •-(,•     hi  th«  i^Mnlon  (jftrrln^n  from   ' 

•iriv«-,  Mfifl    ptillinj/  on  nn  n\,ninm  .1  iiriioinil      ' 
weight  In  ^  v»iin  I'liilcnvor  t,o  inkfi  out  ilio  nlnr.k,      i  icli  i   n.-   •  noi 
Min^m^nf,  \.\\H  ropn  w««»r«  out,  v  .  |  )-'). 

Idly,  And  morn  fM-'jin-nfly  pAfU  wt  ilia  uplift*,      It,  I*  <l(»-i<  >.i.  •   •" 

nil  0MM  oi  MHntlMftlon  f/i  IKI  Armr>^«  MM    M  I   llii(  "'• 

i<   M)(!^  of  DM    '"CM  ftliftll  !»<•  on  ilin  np|"  '  t  "*     f  "••   i" 


HAND  ,.,,1,1, 


Mia 


lltn  .    ,n,  f<  ,  ||HJ    ih,t     y  .     ol     •  ••'"  ••  '      •  •'',.     I*  ••     '•'•      »»  'II  il 

.  ipp,,.  ..  i.  ,  i,  i.  ofchi  '    "  i"  it  In  motion      MI,-  woi  kluj     "  •  »»  i«» 

I',  Mill,  |    ,      .Ml       (I     ll'pl>      lit.  Mil,  I       |1  '   |\l  |"    • 

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MOO    IV.  -t     p.  i     nmmi.  -,    iin.l    Ilih    MJUMM!    j»l\«       bill     '-'^l   IVKUlUllI 

ii    r      rii,  pi  ,,  HI  •!  i,  .mi  to  iii,-  itiuuhi  i  ni  ,.•!  \\\  kyi 

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muni-  i    -'i     «-|"       ,  •  •  ,  ,  .1      ill.  ........  .-oihl 

MI  i\  be  ntliti  !  '"•'  '!'•  'i"^  '"  •  li  d  "'''•       '  ''  '" 

ii..ni.i    A(||    b<     I-  H  Hum    lo  .1  i  >  00 

ili'im. 
III    ili 


|»«>\N  '  «      i.    v    ,      .MM.-   nx    ....  , 


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III,-   ili'inirli-i     .<!      I  l,<      i    >pi 


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Mil,  MM 

814 


HANDBOOK    ON    ENGINEERING. 


TO  TEST  THE  PURITY  OF  ROPE. 

A  simple  test  for  the  purity  of  manila  or  sisal  rope  is  as  fol- 
lows :  — 

Take  some  of  the  loose  fiber  and  roll  it  into  balls  and  burn 
them  completely  to  ashes,  and,  if  the  rope  is  pure  manila,  the  ash 
will  be  a  dull  grayish  black.  If  the  rope  be  made  from  sisal  the 
ash  will  be  a  whitish  gray,  and  if  the  rope  is  made  from  a  com- 
bination of  manila  and  sisal  the  ash  will  be  of  a  mixed  color. 

WIRE  ROPE  DATA. 


HOISTING    ROPE. 


PATENT    FLATTENED    STRAND. 


HERCD- 
LES. 


foo 
s. 


II 

br  flo 


13.5 

22.5 

32 

40.5 

56 

r,7 

84 
124 
168 
211 

'2(50 


CRUCI- 
BLE. 


per  fo 
cents. 


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181 

24 

30 

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86 

121 

144 

182 


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140  i  120 
176  1 1 152 


9 
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19    WIRE    ROUND    STRAND. 


HERCU- 
LES. 


is* 

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CKUCI- 
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rP 


12.5 

20 

29 

36 

50 

60 

77 
113 
157 
191 
238 


8.8 

13.6 

19.4 

26 

34 

42 

50 

72 

96 
124 
156 


*>.£  = 


HANDBOOK    ON    ENGINEERING.  815 


ALTERNATING   CURRENT  MACHINERY. 

CHAPTER     XXIX. 
THE  PRINCIPLES  OF  ALTERNATING  CURRENTS. 

The  actions  of  alternating  currents  are  not  so  easily  under- 
stood as  those  of  continuous  currents  and  to  most  men  not 
familiar  with  the  subject  they  appear  to  be  a  mystery  that  can 
only  be  fathomed  by  those  who  are  well  versed  in  the  higher 
branches  of  mathematics.  As  a  matter  of  fact,  when  we  once 
get  on  the  right  track,  alternating  current  actions  present  no  more 
difficulty  to  the  man  of  fair  mental  ability,  who  is  willing  to  work 
to  learn,  than  the  more  simple  continuous  current  actions.  What 
makes  alternating  currents  difficult  to  .understand  is,  that  in  con- 
sequence of  the  ever-changing  strength  of  Mie  current,  inductive 
actions  are  developed  that  react  upon  the  uirrent  itself  so  that  it 
becomes  impossible  to  determine  the  magnitude  of  the  current, 
the  e.m.f.  or  the  energy  flowing  in  the  circ'iit  by  the  simple  rules 
used  for  continuous  currents.  As  the  strength  of  an  alternating 
current  is  constantly  changing  the  magnitude  of  the  inductive 
actions  is  constantly  changing,  and  this  fact  further  increases 
the  difficulty  of  the  subject. 

In  studying  the  principles  of  continuous  currents  we  learn  that 
when  a  conductor  is  moved  across  a  magnetic  field  an  e.m.f.  is 
developed  in  it ;  and  thus  we  understand  the  operation  of  a  gen- 
erator, as  we  know  that  when  the  armature  revolves,  it  carries 
the  conductors  upon  its  surface  through  the  magnetic  flux  that 
issued  from  the  poles  of  the  field.  We  further  learn  that  iiuis- 


816  HANDBOOK    ON    ENGINEERING. 

much  as  the  magnitude  of  the  e.m.f.  is  increased  by  increasing 
the  strength  of  the  magnetic  flux,  or  the  number  of  conductors 
on  the  armature  or  the  velocity  of  rotation,  that  one  or  all  these 
factors  must  be  increased  to  increase  the  voltage.  Thus  we  come 
to  consider  that  to  induce  a  high  e.m.f.  we  must  have  a  strong 
magnetic  field.  Now  one  of  the  first  things  that  the  student  of 
alternating  currents  finds  out  is  that  in  an  alternating  current 
circuit,  the  strongest  e.m.f.  induced  by  the  action  of  the  current 
itself,  comes  at  the  very  time  when  the  magnetic  field  is  the 
weakest,  and  this  appears  to  him  to  completely  upset  all  the 
principles  of  continuous  currents;  but  in  reality  it  does  not. 
To  be  able  to  get  over  this  stumbling  block  successfully  it  is 
necessarv  to  realize  that  the  magnitude  of  the  e.m.f.  induced  in 
a  conductor  that  is  moved  through  a  magnetic  field  is  not  depend- 
ent upon  the  strength  of-  the  magnetic  field,  but  upon  the  rate, 
or  rapidity  with  which  the  conductor  cuts  the  magnetic  flux. 
Now  it  so  happens  that  in  a  continuous  current  generator,  the 
rapidity  with  which  the  conductors  cut  the  magnetic  flux  increases 
with  increase  in  the  strength  of  the  magnetic  field,  or  the  velocity 
of  rotation,  and  thus  it  comes  about  that  in  this  case,  the  increase 
in  the  induced  e.m.f.  appears  to  be  due  to  increase  in  armature 
velocity  or  field  strength  when  in  reality  it  is  due  to  increase  in 
the  rate  at  which  the  conductors  cut  through  the  magnetic  flux. 
The  magnetic  flux  developed  by  an  alternating  current  alternates 
precisely  as  the  current  does,  and,  as  will  be  clearly  explained 
presently,  this  magnetic  flux  cuts  through  any  conductors  in  its 
path,  and  the  rate  at  which  it  cuts  them  is  the  greatest  at  the  in- 
stant when  the  direction  of  the  flux  is  changing,  and  this  is  the 
instant  when  the  flux  is  nothing,  so  that  the  e.m.f.  induced  by 
the  magnetic  flux  developed  by  an  alternating  current  is  the 
greatest  at  the  very  instant  when  the  magnetic  field  has  a  zero 
strength.  The  foregoing  facts  can  be  made  more  clear  by  refer- 
ence to  diagrams. 


HANDBOOK    ON    ENGINEERING. 


817 


Fig*  I  is  a  simple  diagram  that  can  be  taken  to  represent  a  genera- 
tor, either  of  continuous  or  alternating  currents.  The  dark  circles 
A  A,  B  B  and  C  C  represent  the  sides  of  three  loops  of  wire 
which  may  be  regarded  as  wound  upon  the  surface  of  an  armature. 


JV 

jjz 


Fig.   1, 


The  vertical  lines  represent  a  magnetic  flux  passing  between  the 
Held  poles  Pand  JV.  If  the  armature  upon  which  the  three  loops 
are  mounted  is  rotated,  e.m.fs.,  will  be  induced  in  each  one  of 
the  loops,  but  the  magnitude  of  these  e.m.fs.  will  not  be  the 
same.  If  we  take  the  instant  when  the  loops  are  in  the  position 
shown,  the  e.m.f .  in  A  A  will  be  zero,  while  that  in  C  C  will  be 
the  highest  and  that  in  B  B  will  be  seven-tenths  of  tb at  in  G  C. 
Now  all  these  coils  rotate  at  the  same  velocity  being  mounted  upon 
the  same  armature,  and  all  move  through  a  magnetic  field  of  the 
same  strength,  yet,  in  A  A  no  e.m.f .  is  developed  while  in  B  B  the 
e.m.f.  is  only  seven-tenths  of  that  developed  in  C  C.  The 
question  is,  why  this  difference?  The  answer  is,  that  while  loops 
A  A  move  just  as  fast  as  C  C  they  do  not  cut  the  magnetic  flux 

52 


818  HANDBOOK    ON    ENGINEERING. 

because  they  are  moving  in  a  direction  parallel  with  the  lines  of 
force,  the  vertical  lines,  hence,  the  rate  at  which  the  magnetic 
flux  is  cut  by  them  is  zero,  therefore  the  e.m.f.  developed  is  zero. 
In  B  B  the  e.m.f.  is  seven-tenths  of  that  developed  in  G  (7, 
because  the  sides  of  this  loop  are  moving  in  a  direction  that  is 
not  directly  across  the  magnetic  flux,  but  forms  an  angle  of  45 
degrees  with  it,  so  that  their  actual  velocity  in  a  direction  parallel 
with  A  A  is  seven-tenths  of  the  velocity  of  C  C  in  this  same 
direction. 

From  the  foregoing  it  will  be  seen  that  when  we  get  down  to 
a  close  examination  of  Fig.  1  we  find  that  the  magnitude  of 
the  e.m.f.  developed  in  the  several  loops  is  directly  proportional 
to  the  rate  at  which  the  sides  of  the  loop  cut  through  the 
magnetic  flux. 

Let  us  now  consider  Fig.  2.  In  this  diagram,  circle  A  repre- 
sents a  wire,  seen  end  on,  through  which  an  alternating  current  is 
flowing.  An  alternating  current  is  one  that  flows  first  in  one 
direction,  and  then  in  the  opposite  direction,  and  continues 
changing  the  direction  in  which  it  flows  at  regular  intervals  of 
time.  Now  it  is  self-evident  that  if  a  current  flows  through  a 
wire  in  alternate  directions,  it  must  stop  flowing  in  one  direction 
before  it  can  flow  in  the  opposite  direction,  that  is  at  the  instant 
when  the  direction  of  flow  is  changing,  there  can  be  no  current. 
Such  being  the  case,  when  the  current  begins  to  flow  in  either 
direction,  it  must  increase  in  strength  gradually  up  to  a  certain 
point,  and  then  begin  to  decrease,  so  as  to  reduce  to  nothing  at 
the  instant  when  the  direction  of  flow  changes.  As  is  explained 
in  the  section  on  continuous  currents,  when  a  current  of  elec- 
tricity flows  through  a  wire,  a  magnetic  flux  is  developed  around 
the  wire  and  this  can  be  represented  by  lines  of  force  drawn  in 
the  form  of  circles,  as  in  Fig.  2.  If  there  is  no  current  flowing 
through  the  wire  there  is  no  magnetic  flux,  therefore,  if  wo 
consider  the  instant  when  a  current  begins  to  flow,  we  can  imagine 


HANDBOOK    ON    ENGINEERING.  819 

that  at  this  instant  the  magnetic  flux  begins  to  expand  outward 
from  the  wire,  and  since  the  circular  lines  are  drawn  to  represent 
this  flux  we  can  assume  that  these  expand  outward,  like  the  rip- 
ples on  the  surface  of  a  pond  when  a  pebble  is  thrown  into  the 
water.  So  long  as  the  current  flowing  through  the  wire  increases 
in  strength,  just  so  long  will  the  magnetic  circles  of  force  expand, 
but  when  the  current  reaches  its  greatest  strength  the  circular 
lines  of  force  will  become  stationary,  and  will  remain  so  if  the 
current  remains  at  its  maximum  strength;  but  if  the  current 
begins  to  reduce  in  strength  as  soon  as  it  reaches  its  maximum, 
then  the  circular  lines  of  force  will  begin  to  contract  immediately 
after  they  stop  expanding,  just  as  a  swing  will  begin  to  move 
backward  the  instant  it  stops  swinging  forward. 

If  the  circles  B  and  C  in  Fig.  2  represent  two  wires  parallel 
with  J.,  it  is  evident  that  the  magnetic  circles  of  force  when  they 
move  outward  from  A  will  cut  through  B  and  C  in  one  direction, 
and  when  they  contract  back  upon  A  they  will  cut  through  these 
two  wires  in  the  opposite  direction.  When  these  circular  lines 
of  force  cut  through  the  wires  B  G  they  will  induce  e.m.fs.  in  the 
latter,  and  if  these  e.m.fs.  are  positive  when  the  lines  of  force  ex- 
pand, they  will  be  negative  when  the  lines  contract.  When  the 
current  reaches  its  maximum  strength  and  the  circular  lines  of 
force  become  stationary  for  an  instant,  they  will  not  cut  the  wires 
B  and  C  and  at  this  instant  there  will  be  no  e.m.f.  induced  in 
these  wires.  Now  the  circular  lines  of  force  become  stationary 
at  the  very  instant  when  the  current  flowing  through  the  wire 
reaches  its  greatest  strength  and  is  on  the  point  of  reducing,  so 
that  at  this  instant  the  e.m.f.  induced  in  the  wires  B  and  C  is  zero. 

The  highest  e.m.f.  induced  in  B  and  C  occurs  at  the  instant 
when  the  current  flowing  through  A  is  changing  its  direction,  or,  in 
other  words,  at  the  instant  when  there  is  no  current.  Just 
before  the  current  reduces  to  zero,  the  circular  lines  of  force 
are  contracting  upon  wire  A,  and  the  instant  after  the  cur- 


820  HANDBOOK    ON    ENGINEERING. 

rent  reduces  to  zero  and  changes  its  direction,  these  lines 
of  force  will  be  expanding  so  that  in  the  first  case  the  lines 
of  force  will  sweep  over  wires  B  and  G  in  a  direction  toward 
A,  and  in  the  second  case  they  will  sweep  over  these  wires  in  a 
direction  away  from  A.  From  this  fact  it  might  be  inferred  that 
the  e.m.f.  induced  in  the  two  cases  would  be  in  opposite  direc- 
tions, but  this  is  not  so,  owing  to  the  fact  that  the  lines  of  force 
change  in  direction  when  the  current  changes,  so  that  if  while 
contracting  they  are  directed  clockwise,  as  soon  as  they  begin  to 
expand  they  will  be  directed  counter  clockwise.  As  a  result  of 
this  change  in  the  direction  of  the  lines  of  force  when  they  change 
from  contracting  to  expanding,  the  e.m.fs.  induced  in  B  and  C 
are  in  the  same  direction  before  the  lines  stop  contracting  and 
after  they  begin  to  expand.  The  circular  lines  of  force  stop  con- 
tracting and  begin  to  expand  at  the  same  instant,  so  that  the 
inductive  action  developed  by  the  contracting  lines  is  followed  up 
without  a  break  by  the  expanding  lines.  In  alternating  currents 
such  as  are  actually  used  in  practice,  the  rate  at  which  the 
strength  of  the  current  changes  is  the  greatest  when  it  is  just 
beginning  to  grow,  and  when  it  is  reduced  almost  to  zero,  and  on 
this  account  the  highest  e.m.f.  induced  in  wires  B  and  C  occurs 
at  the  instant  when  the  direction  of  the  current  is  changing,  that 
is,  when  the  current  is  zero.  Alternating  currents  can  be  de- 
veloped in  which  the  rate  of  change  in  the  current  is  not  the 
greatest  just  when  they  begin  to  grow  and  when  they  are  reduced 
nearly  to  zero  and  with  such  currents  the  highest  e.m.f.  induced 
in  wires  B  and  C  would  not  come  at  the  instant  when  the  current 
is  zero,  but  would  come  at  the  instants  when  the  change  in  the 
current  is  the  most  rapid. 

In  every  kind  of  alternating  current,  however,  the  instant  when 
the  e.m.f.  induced  in  B  and  C  is  zero  is  the  instant  when  the 
current  reaches  the  maximum  value,  and  begins  to  decrease, 
for  this  is  the  only  instant  when  the  circular  lines  of  force  are 


HANDBOOK    ON    ENGINEERING. 


821 


immovable ;  it  being  the  instant  when  they  are  about  to  change 
from  expanding  to  contracting,  while  still  flowing  in  the  same 
direction.  When  the  current  becomes  zero,  the  lines  of  force 
change  from  contracting  to  expanding  but  at  this  instant  they 
also  change  their  direction  so  that  the  new  expanding  circular 
lines  of  force  take  up  the  work  if  inducing  an  e.m.f.  in  the  wires 
B  and  (7  at  the  very  point  where  the  contracting  lines  leave  off. 

The  circular  lines  of  force  developed  by  the  current  flowing 
in  A  cut  through  this  wire  as  well  as  through  B  and  (7,  hence, 
they  induce  an  e.m.f.  in  A;  that  is  an  alternating  current  induces 
an  e.m.f.  in  its  own  circuit  as  well  as  in  adjoining  circuits.  The 
action  upon  adjoining  wires  is  called  mutual  induction,  and  that 
upon  its  own  wire  is  called  self-induction.  These  e.m.fs.  act  in 
a  direction  opposite  to  that  of  the  current  that  induces  them. 

The  relations  between  alternating  currents  and  e.m.fs.  can  be 
shown  by  means  of  diagrams,  the  simplest  of  which  are  con- 


FigJS 


structed  in  the  manner  shown  in  Fig.  3.  In  diagrams  of  this 
type  the  line  0  T  represents  time,  thus  if  a  point  is  assumed  to 
move  from  0  in  the  direction  of  T  at  a  uniform  velocity  of  say 
one  foot  per  second,  then  a  length  of  one  inch  will  represent  an 
interval  of  time  of  one-twelfth  of  a  second.  Distances  measured 
in  the  vertical  direction,  along  0  $  represent  the  magnitude  of 


822  HANDBOOK    ON   ENGINEERING. 

the  current  or  e.m.f.  Positive  currents  and  e.m.f.  are  indicated 
above  the  time  line  0  T  and  negative  currents  and  e.m.fs.  below 
this  line.  Thus  the  wave  line  A  A  A  can  represent  an  alternating 
current  or  e.m.f.  or  an  alternating  magnetic  flux.  This  curve  it 
will  be  seen  is  above  0  T  from  Oto6,  and  below  0  T  from  b 
to  d,  being  again  above  from  d  to  T.  The  two  sections  of  the 
curve  from  0  to  d  constitute  one  cycle,  or  two  alternations.  The 
portions  between  the  lines  0  a,  a  5,  b  c,  c  d  are  called  quarter 
cycles  or  quarter  periods.  The  time  from  0  to  d  is  called  one 
period,  and  if  this  is  equal  to  one-tenth  of  the  distance  that 
represents  one  second,  then  there  are  ten  periods  to  one  second. 
This  fact  is  indicated  by  saying  that  the  periodicity  of  the  current 
is  ten,  or  that  its  frequency  is  ten.  The  frequency  of  alternating 
currents  in  common  use  ranges  between  20  and  130. 

The  curve  A  A  in  Fig.  3  represents  a  current  or  e.m.f .  that 
increases  or  decreases  at  a  certain  rate,  but  for  a  current  varying 
at  some  other  rate  it  would  be  necessary  to  use  a  curve  of  differ- 
ent shape  to  correctly  represent  it.  Thus  if  the  current  does  not 
increase  so  fast  when  rising  from  the  zero  value,  but  increases 
faster  when  nearing  its  maximum  value  we  will  require  a  modifica- 
tion of  the  curve  such  as  is  indicated  by  .B,  in  which  the  slope  is 
more  gradual  on  the  start,  and  near  the  middle  becomes  more 
steep.  If  on  the  other  hand  the  current  increases  more  rapidly 
on  the  start,  and  less  rapidly  as  it  approaches  the  maximum  value, 
we  will  have  to  use  a  curve  something  like  C  which  is  steeper  at 
the  ends  and  flatter  at  the  middle. 

The  actual  form  of  curve  required  to  correctly  represent  an 
alternating  current  depends  upon  the  rate  at  which  the  current 
varies,  and  this  rate  depends  upon  the  construction  of  the  machine 
in  which  it  is  generated.  For  the  purpose  of  simplifying  calcula- 
tions it  is  necessary  to  assume  that  the  rate  of  variation  of  a  cur- 
rent is  such  that  it  can  be  represented  in  a  diagram  such  as  Fig- 
3  by  some  form  of  curve  that  can  be  drawn  in  accordance  with 


HANDBOOK    ON    ENGINEERING. 


823 


some  fixed  rule.  The  curve  A  A  is  of  circular  form,  but  there 
are  few  alternating  current  generators  that  develop  currents  that 
such  a  curve  can  properly  represent. 

If  a  current  alternates  in  equal  intervals  of  time,  and  the  rate 
of  variation  is  the  same  when  it  is  flowing  negatively  as  when  it  is 
flowing  positively,  then  it  can  be  represented  by  a  curve  that  is 
of  symmetrical  construction,  such  as  A  A  in  which  the  intervals  of 
time  0  &,  b  d  are  equal  and  the  curves  above  the  line  0  T  are  of 
the  same  shape  as  those  below  it.  Such  a  current  is  called  a 
symmetrical  periodic  current,  and  it  is  the  only  kind  with  which  we 
have  to  do  in  practice.  It  can  be  readily  understood,  however, 
that  the  current  can  be  far  from  regular,  that  is,  the  time  during 
which  it  flows  positively  can  be  more  or  less  than  the  time  during 
which  it  flows  negat'  Ty,  and  the  rate  of  variation  in  the  two 


instances  can  be  different.  The  curves  in  Figs.  4  and  5  illustrate 
currents  of  this  kind.  In  Fig.  4  the  positive  impulses  of  the  cur- 
rent are  longer  than  the  negative,  as  is  shown  by  the  greater 
length  of  lines  0  a,  b  c  as  compared  with  a  b.  It  will  also  be 
seen  that  the  rate  of  variation  is  different  as  is  indicated  by  the 
difference  in  the  form  of  the  portions  A  A  and  B  B  of  the 
curve.  In  Fig.  5  the  irregularity  is  still  greater,  as  all  the  time 
intervals  Oa,  a  6,  b  c,  c  cZ,  are  different,  as  are  also  the  portions 
A  B  C  D  E  of  the  curve. 


824 


HANDBOOK    ON    ENGINEERING. 


The  alternating  currents  developed  by  alternating  current 
generators  have  such  a  rate  of  variation  that  they  can  be  repre- 
sented in  diagrams  by  means  of  what  is  known  as  a  sine  curve. 


s 


This  curve  is  not  a  perfectly  true- representation  of  practical 
alternating  currents,  but  it  comes  so  near  to  it  that  calculations 
based  upon  the  assumption  that  the  sine  curve  represents  the  actual 


variation,  do  not  depart  from  the  truth  by  more  than  two  or  three 
per  cent,  and  in  some  cases  less  than  that.  As  the  sine  curve  is 
commonly  used  to  represent  alternating  currents  we  will  show 


HANDBOOK    ON    ENGINEERING.  825 

how  it  is  constructed  by  the  aid  of  Fig.  6.  In  this  diagram  dia- 
metrical lines  a  b  c  are  drawn  on  the  circle  J3,  dividing  it  into 
any  desired  number  of  equal  parts.  A  distance  0  T  on  the  hor- 
izontal line  is  divided  into  an  equral  number  of  equal  parts  and 
perpendicular  lines  a  a  are  drawn  at  these  divisions.  From  the 
points  where  the  liness  a  b  c  cut  the  circle  lines  are  drawn  parallel 
with  0  T  as  shown  at  e  f  g  and  the  points  where  these  cut  the 
corresponding  perpendicular  lines  a  a  form  points  of  the  sine 
curve  A  A.  The  distance  0  T  can  be  made  anything  desired 
without  affecting  the  character  of  the  curve,  the  only  difference 
being  that  if  it  is  short  the  curve  will  be  more  pointed  than  if  it 
is  long. 

One  reason  why  it  is  assumed  that  alternating  currents  vary 
in  accordance  with  a  sine  curve  is  that  if  the  variation  is  at  this 
rate  the  e.m.f.  induced  by  the  magnetic  flux  developed  by  the 
current  will  also  vary  in  accordance  with  the  sine  curve,  so  that 
the  current,  the  magnetization  and  the  induced  e.m.f.  can  be  rep- 
resented by  sine  curves,  and  thus  the  process  of  calculating  the 
effect  of  the  induced  e.m.f.  upon  the  strength  of  the  current  can 
be  greatly  simplified. 

By  looking  at  Fig.  1  it  can  be  seen  at  once  that  if  the 
loop  A  A  is  revolved  at  a  uniform  velocity,  and  the 
magnetic  field  between  the  poles  P  and  N  is  of  uniform 
strength  at  every  point,  the  e.m.f.  induced  in  A  A  will 
vary  in  strict  accordance  with  the  variations  of  the  sine 
curve  A  A  of  Fig.  6,  for  in  the  position  A  A  the  e.m.f.  will  be 
zero,  and  in  position  C  C  it  will  be  the  maximum,  while  in  any  in- 
termediate position  such  as  B  B  it  will  be  equal  to  the  actual  velocity 
of  the  sides  of  the  loop  measured  in  the  direction  parallel  with 
AA  ,  and  this  velocity  is  equal  to  the  distance  of  the  side  of  the 
loop  from  the  horizontal  line  A  A.  Now  the  height  of  the  sine 
curve  A  A  in  Fig.  6  at  any  point  is  also  equal  to  the  distance  from 
the  end  of  the  corresponding  line  in  circle  B  from  the  horizontal 


HANDBOOK    ON   ENGINEERING. 


line,  that  is,  the  distrance  e  e'  from  the  horizontal  line  to  the  curve 
is  the  same  as  the  distance  e  e  on  the  circle. 

The  complete  sine  curve  from  0  to  T  is  traced  by  following  the 
rotation  of  the  radius  of  the  circle  through  one  complete  revolu- 
tion. On  that  account  this  distance  0  T  is  taken  to  represent  one 
revolution,  and  is  divided  into  360  degrees,  the  same  as  the 
circle.  Half  the  distance,  or  0  d,  is  equal  to  180  degrees,  and 
one-quarter  the  distance  is  90.  The  vertical  lines  a  a  in  Fig.  6 
are  30  degrees  apart. 

The  way  in  which  sine  curves  are  used  to  represent  alternat- 
ing currents  and  e.m.fs.  is  shown  in  Fig.  7.  In  this  diagram, 


let  the  curve  A  represent  an  alternating  current  flowing  through  a 
wire.  As  is  fully  explained  in  the  foregoing,  this  current  will 
develop  an  alternating  magnetic  flux,  and  this  flux  will  increase 
and  decrease  as  the  current  increases  and  decreases,  that  is,  it 
will  keep  in  time  with  the  current,  or  in  step  with  it,  as  it  is  com- 
monly expressed.  Such  being  the  case,  the  curve  A  can  be  used 
to  represent  the  magnetic  flux  as  well  as  the  current,  providing 
we  assume  a  proper  scale  for  both.  Looking  at  the  half  circle  to 
the  left  of  the  figure,  it  will  be  seen  that  curve  A  is  described  by 


HANDBOOK    ON    ENGINEERING.  827 

a  radius  rotating  around  the  middle  circle.  Remembering  what 
was  said  in  connection  with  Fig.  2  as  to  the  time  relation  between  the 
magnetic  flux  and  the  e.m.f .  induced  thereby,  we  will  realize  that 
at  the  instant  0  when  the  flux  is  zero,  the  induced  e.m.f.  must 
be  at  the  maximum  value,  and  it  will  act  in  opposition  to  the 
e.m.f.  that  drives  the  current  through  the  wire,  hence,  in  the 
diagram,  it  will  have  to  be  drawn  below  line  0  T.  Let  the  maxi- 
mum value  of  this  induced  e.m.f.  be  equal  to  0  c,  then  for  all 
other  values  it  will  be  correctly  represented  by  the  sine  curve  .B, 
which  is  traced  by  the  rotation  of  the  radius  of  the  inner  circle. 

At  the  instant  of  time  0,  the  magnetic  flux  is  zero,  hence  the 
radius  of  the  middle  circle  from  which  curve  A  is  traced  must  be 
in  the  direction  of  line  0  T.  At  this  same  instant  the  induced 
e.m.f.  is  at  the  maximum  value  hence  the  radius  that  traces 
curve  B  must  be  in  the  vertical  position  parallel  with  O  c.  From 
this  we  see  that  in  relation  to  time  the  curves  A  and  B  that  repre- 
sent the  magnetic  flux  and  the  induced  e.m.f.  are  one-quarter  of 
a  cycle  apart,  that  is  the  induced  e.m.f.  is  90  degrees  behind  the 
magnetization,  and  also  90  degrees  behind  the  current  that  flows 
through  the  wire. 

No  kind  of  electric  current,  whether  continuous  or  alternating, 
can  flow  through  a  circuit  unless  there  is  an  e.m.f.  to  drive  it, 
and  this  e.m.f.  must  be  sufficient  to  impel  the  current  against 
all  resistances  of  any  kind  that  it  may  encounter.  The  e.m.f. 
that  impels  a  current  through  an  alternating  current  circuit  is 
called  the  impressed  e.m.f.  In  Fig.  7  it  is  evident  that  the 
impressed  e.m.f.  must  be  sufficient  not  only  to  overcome  the 
actual  resistance  that  opposes  the  flow  of  the  current  represented 
by  curve  A,  but  also  sufficient  to  overcome  the  opposing  action  of 
the  induced  e.m.f.  represented  by  curve  B.  Now  the  e.m.f. 
required  to  overcome  the  resistance  that  opposed  the  flow  of  the 
current  can  be  represented  by  the  curve  A,  in  precisely  the  same 


828  HANDBOOK    ON    ENGINEERING. 

way  as  this  curve  represents  the  magnetization ;  hence,  the  curve 
C  which  represents  the  impressed  e.m.f .  must  at  every  point  be 
equal,  in  height,  from  the  line  0  T,  to  the  sum  of  the  heights  of  the 
curves  A  and  .B,  when  these  two  curves  are  on  opposite  sides 
of  0  T,  or  to  their  difference  when  they  are  on  the  same  side.  At 
the  instant  0  it  is  clear  that  as  the  current  is  zero,  the  impressed 
e.m.f.  C  must  be  of  the  value  0  c'  to  balance  the  induced  e.m.f. 
B  for  if  it  were  not,  there  would  be  a  current  flowing  negatively 
under  the  influence  of  e.m.f.  B.  At  any  instant  between  C  and 
d,  the  impressed  e.m.f.  C  must  be  equal  to  the  sum  A  and  5,  that 
is,  the  distance  from  C  to  the  time  line  0  T  must  be  equal  to  the 
distance  between  the  curves  .4  B  measured  on  the  same  vertical  line. 
At  the  instant  d  the  induced  e.m.f.  is  zero,  hence  the  impressed 
e.m.f.  is  equal  to  the  distance  of  curve  A  above  line  0  T.  For 
any  interval  of  time  between  d  and  e,  the  impressed  and  the  in- 
duced e.m.fs.  are  acting  together,  so  that  the  first  named,  that  is, 
curve  (7,  need  only  be  equal  to  the  difference  between  A  and  B. 

By  studying  the  diagram  Fig.  7  it  will  be  seen  that  the  curve 
O,  which  represents  the  impressed  e.m.f.,  is  described  by  the 
rotation  of  the  radius  of  the  outer  circle  at  Z>,  and  in  order  that 
this  e.m.f.  may  have  the  value  of  0  c'  at  the  instant  0,  it  is  nec- 
essary for  the  describing  radius  at  this  instant  to  be  in  the  posi- 
tion 6.  From  this  it  will  be  seen  that  the  impressed  e.m.f.  is  not 
in  time  with  the  current  but  in  advance  of  it  by  a  time  interval 
that  is  equal  to  the  angle  formed  by  the  radius  b  with  the  line 
0  T. 

If  two  alternating  currents,  e.m.f.  or  magnetic  fluxes  are 
in  time  with  each  other  they  are  said  to  be  in  phase,  but  if  they 
are  not  in  time  they  are  out  of  phase.  In  Fig.  7  the  current,  the 
impressed  e.m.f.  and  the  induced  e.m.f.  are  out  of  phase  with  each 
other.  The  impressed  e.m.f.  leads  the  current,  and  the  latter 
leads  the  induced  e.m.f.  This  relation  is  also  expressed  by  say- 


HANDBOOK    OX    ENGINEERING. 


829 


ing  that  the  current  lags  behind  the  im- 
pressed e.ra.f.  and  the  induced  e.m.f. 
lags  behind  the  current.  The  current 
and  the  impressed  e.m.f.  can  never  be 
out  of  phase  by  an  angle  as  great  as  90 
degrees,  but  the  phase  difference  can  be 
any  angle  less  than  this.  The  induced 
e.m.f.  is  always  90  degrees  out  of  phase 
with  the  current.  The  induced  e.m.f. 
in  the  circuit  in  which  the  current  flows 
is  called  the  self-induction. 

The  relations  between  the  impressed 
e.m.f.,  the  current  and  the  self-induc- 
tion both  in  magnitude  and  phase  are 
clearly  shown  in  Fig.  8,  which  is  simply 
an  enlarged  view  of  the  left  side  of 
Fig.  7.  The  radius  A  of  the  outer 
circle  is  the  impressed  e.m.f.  The 
radius  B  of  the  middle  circle  is  the  cur- 
rent, and  the  radius  C  of  the  inner 
circle  is  the  self-induction.  The  magnitude  of  any  one  of  these 
three  quantities  at  any  instant  of  time  is  equal  to  the  distance 
from  the  end  of  the  line  to  the  horizontal  line.  The  radius  B 
which  represents  the  current  is  on  the  horizontal  line,  hence  the 
current  at  the  instant  represented  by  the  diagram  is  zero.  The 
self-induction  G  has  a  value  at  this  instant  equal  to  the  length  of 
the  ime,  that  is,  it  is  at  the  maximum  value,  and  as  it  is  below 
the  horizontal  line  it  is  negative.  The  impressed  e.m.f.  A,  has 
the  value  of  a  a,  and  being  above  the  horizontal  line,  it  is  positive. 
The  phase  relation  and  also  the  magnitude  of  these  quantities  is 
also  shown  in  Fig.  9,  which  is  constructed  from  Fig.  8  by  remov- 
ing the  self-induction  to  the  position  of  line  a  a.  From  Fig.  9  it 


Fig.8 


830 


HANDBOOK    ON    ENGINEERING. 


CURRENT. 


Figs 


RESISTANCE. 

Fi/JO 


can  be  seen  that  if  we  know  two 
of  the  quantities  we  can  always 
determine  the  other  one  by  sim- 
ply constructing  a  right  angle 
triangle. 

The  self-induction  acts  tc 
oppose  the  flow  of  current, 
hence  it  is  equivalent  to  th( 
addition  to  a  certain  amount  oi 
resistance  to  the  circuit,  but.a;- 
can  be  seen  from  the  diagrams- 
it  cannot  .be  added  directly, 
after  the  fashion  in  which 
numbers  are  added.  To  add  it 
properly  it  must  be  placed  at 
right  angles  to  the  resistance. 
If  the  self-induction  is  divided 
by  the  strength  of  the  current, 
we  get  a  quantity  that  can  be 
compared  with  the  resistance, 
and  this  quantity  is  called  the 

reactance  and  is  measured  in  ohms  precisely  as  the  resistance  is. 
The  flow  of  current  in  a  continuous  current  circuit  is  opposed 
by  the  resistance  only,  but  in  an  alternating  current  circuit  it  is 
opposed  by  the  resistance  and  the  reactance  and  the  combined 
effect  of  these  two  is  called  the  impedance  of  the  circuit. 

The  relation  between  resistance,  reactance  and  impedance  is 
the  same  as  that  between  impressed  e.m.f.,  current  and  self- 
induction,  and  is  shown  in  Fig.  10. 

The  reactance  multiplied  by  the  current  gives  the  self -induction. 
The  impedance  multiplied  by  the  current  gives  the  impressed 
e.m.f. 


HANDBOOK    ON    ENGINEERING. 


831 


The  resistance  multiplied  by  the  current  gives  the  e.m.f.  in 
phase  with  the  current,  which  is  also  called  the  active  e.m.f. 

A  sine  curve  diagram,  such  as  is  shown  in  Fig. 
7,  serves  very  well  to  enable  the  learner  to  under- 
stand the  relation  between  the  current  and  e.m.fs.  but 
when  this  relation  has  been  fully  mastered,  what  is  known 
as  a  clock  dial  diagram  becomes  more  convenient,  specially 
if  we  desire  to  represent  several  currents  and  their  e.rn.fs.  Fig.  8 
is  virtually  one-half  of  a  clock  dial  diagram.  A  regular  clock 
dial  diagram  to  represent  a  single  alternating  current  is  shown 
in  Figs.  11.  12,  13.  The  radius  A  represents  the  current,  and  is 


Fi/Jg 


Fig.  2 3 


supposed  to  rotate  at  a  velocity  equal  to  the  frequency  of  the 
current.  The  strength  of  the  current  for  any  instant  of  time  is 
obtained  by  measuring  the  distance  from  the  horizontal  line  S  S 
to  the  end  of  the  radius  at  that  particular  instant  as  indicated  by 
line  a  a  in  Fig.  12.  If  A  is  above  the  line  S  S  the  current  is 
positive,  and  if  it  is  below  S  S  the  current  is  negative.  At  the 
instant  when  A  is  in  the  vertical  position,  as  in  Fig.  13,  the 
current  is  at  its  maximum  value,  and  when  A  is  horizontal  as  in 
Fig.  11  the  current  is  zero.  If  we  desire  to  find  the  relation 
between  the  current  and  impressed  e.m.f.  or  the  self-induction, 
we  draw  radial  lines  of  the  proper  length  to  represent  these 
e.m.fs.  and  in  the  proper  angular  position  with  reference  to  the 
current  and  then  assume  them  to  be  locked  together  when  they 


832 


HANDBOOK    ON   ENGINEERING. 


are  rotating  so  that  the  distances  from  the  ends  of  each  one  to 
the  line  S  S  at  any  instant  gives  the  values  of  the  quantities  at 
this  instant. 

Diagrams  of  this  type  are  specially  valuable  for  the  represen- 
tation of  polyphase  currents.  Currents  of  this  type  are  commonly 
spoken  of  as  a  two-phase  current,  or  a  three-phase  current,  or  a 
polyphase  current.  Now  there  are  no  multiplephase  currents. 
What  is  improperly  called  a  two-phase  current  is  a  combination 
or  two  simple  alternating  currents  so  timed  that  they  are  out 
of  phase  with  each  other  by  one  quarter  of  a  period,  or  revolu- 
tion. This  constitutes  a  system  of  two-phase  currents.  Three 
simple  alternating  currents  so  timed  as  to  be  out  of  phase  with 
each  other  by  one-third  of  a  period,  constitute  a  system  of  three 
phase  currents.  In  the  first  case  we  have  two  currents,  and  in 
the  second  we  have  three  currents.  These  currents  in  either 
system  are  connected  so  as  to  act  together  in  the  same  system 
of  circuits.  If  the  phase  relations  are  not  such  as  given  above, 
they  cannot  constitute  true,  two  or  three-phase  systems. 


FijfJj. 


Fif.16 


The  phase  relations  for  the  two-phase  system  are  shown  in  Fig. 
14  and  for  the  three-phase  system  in  Fig.  17.  The  two  currents 
A  B  in  Fig.  14  are  at  right  angles  with  each  other,  and  the  three 
currents  in  Fig.  17  are  120  degrees  apart,  or  one-third  of  a 
period,  or  cycle.  To  obtain  the  values  of  the  two  currents  in 


HANDBOOK    OX    ENGINEERING. 


833 


Fig.  14  at  any  particular  instant,  they  are  rotated  together  as  is 
indicated  in  Figs.  15  and  16.  The  values  will  be  equal  to  the  lines 
a  a  and  b  b.  In  the  same  way  the  values  of  the  three  currents  in 
a  three-phase  system  are  obtained  for  any  instant  as  is  illustrated 
in  Figs.  18  and  19. 

For  the  transmission  of  the  currents  of  a  two-phase  system, 
three  or  four  wires  can  be  used.  In  the  three-phase  system,  if 
the  three  currents  are  equal,  three  wires  are  sufficient,  but  if  these 
currents  are  not  equal  a  fourth  wire  is  required  to  carry  the  surplus 


a 


current  as  it  may  be  called.  When  the  three  currents  of  a  three- 
phase  system  are  equal  it  is  called  a  balance  system,  but  if  they 
are  not  equal  the  system  is  unbalanced.  In  Figs.  17  to  19  the 
three  currents  are  drawn  of  equal  length  and  it  will  be  found  that 
in  every  position  in  which  the  lines  can  be  placed  the  sum  of  the 
two  currents  on  one  side  of  line  S  S  will  be  just  equal  to  the  cur- 
rent on  the  other  side,  so  that  if  the  current  is  flowing  away  from 
the  generator  through  one  wire,  it  will  divide  up  and  return 
through  the  other  two,  and  provide  for  each  wire  just  the  amount 
of  current  required.  Thus  in  Fig.  17  the  current  flowing  in  A  is 
zero,  and  the  positive  current  in  B  is  equal  to  the  negative  current 
in  C.  In  Fig.  18  the  two  positive  currents  a  a  and  b  b  in  lines 
A  B,  are  just  equal  to  the  one  negative  current  in  C,*  and  this 
is  also  the  case  in  Fig.  19. 


834  HANDBOOK    ON    ENGINEERING. 

Unbalanced  three-phase  currents  are  seldom  used,  but  when 
they  are,  a  fourth  wire  is  run  from  the  point  where  the  three 
circuits  A  B  C  are  joined,  to  a  corresponding  point  at  the  genera- 
tor end  of  the  circuit,  and  then  any  excess  or  deficiency  of  current 
that  is  not  provided  for  by  the  three  regular  circuit  wires  is  taken 
through  the  fourth  wire.  The  point  where  the  three  wires  join, 
at  the  center  of  the  circle,  is  called  the  neutral  point,  and  the 
wire  connecting  then  is  the  neutral  wire.  Two  and  three-phase 
systems  are  used  almost  exclusively  for  the  transmission  of  power 
to  great  distances,  and  for  this  work  only  three  wires  are  used. 

Polyphase  systems  can  be  formed  of  any  number  of  currents, 
but  they  would  be  of  no  practical  value,  owing  to  increased  com- 
plications, and  on  that  account  are  not  used.  In  addition  to  the 
one,  two  and  three-phase  systems,  explained  in  the  foregoing,  the 
only  system  that  has  been  used  to  any  extent  is  the  ' '  monocyclic, ' ' 
which  was  introduced  by  the  General  Electric  Company.  This 
system  may  be  described  as  a  sort  of  cross  between  the  single 
phase  and  the  polyphase  systems.  It  consists  of  two  currents, 
90  degrees  out  of  phase,  just  as  in  a  two  phase  system,  but  in- 
stead of  the  two  currents  being  equal,  one  of  them  is  four  times 
the  strength  of  the  other.  The  armature  coils  of  the  generators 
that  furnish  these  currents  are  so  connected  with  each  other 
that  the  two  currents,  as  fed  into  the  line  wires,  constitute  an 
unbalanced  three-phase  system.  This  arrangement  of  the  generator 
coils  will  be  found  more  fully  explained  in  the  section  on  ' '  Alter- 
nating Current  Generator,"  and  the  object  of  the  "  monocyclic  " 
system  will  be  found  explained  in  the  section  on  "  Transmission 
Systems." 

Inductive  Action  in  Alternating  Current  Circuits.  —  In  Fig.  20 
let  G  represent  an  alternating  current  generator  that  impels  an 
alternating  current  through  the  circuit  A  A.  This  current  as 
already  explained  will  develop  a  magnetic  flux  around  the  wire 
such  as  is  indicated  at  C  D.  This  flux  will  develop  a  self-indue- 


HANDBOOK    ON    ENGINEERING.  835 

tive  e.m.f .  in  the  circuit  and  thus  retard  the  current,  so  that  the 
actual  amount  of  current  flowing  will  be  less  than  it  would  be  in 
a  continuous  current  circuit  acted  upon  by  an  impressed  e.m.f.  of 
the  same  magnitude.  As  will  be  noticed,  the  direction  of  the  flux 
at  C  and  D  is  such  that  they  oppose  each  other,  that  is  the  lines 
C  and  D  flow  through  the  space  between  the  two  sides  of  the  loop 
A  A  in  opposite  directions,  and  on  that  account  the  lines  G  can 
only  extend  to  the  center  of  the  space,  while  lines  D  will  occupy 
the  upper  half.  This  being  the  case  it  is  evident  that  if  the  cir- 
cuit wires  are  brought  closer  together  as  indicated  by  the  lines 
B  J3,  the  magnitude  of  the  magnetic  flux  that  will  surround  each 
wire  will  be  correspondingly  reduced  as  is  indicated  by  the  lines  a  a. 
The  self -inductive  e.m.f.  developed  in  the  circuit  will  be  propor- 
tional to  the  magnitude  of  the  flux  that  surrounds  the  wire,  hence 
the  nearer  the  two  sides  are  brought  to  each  other  the  less  the ' 
self-induction,  and  if  the  two  wires  could  be  placed  side  by  side 
the  inductive  effect  would  be  practically  nothing.  From  this  it 


A 


wmr 


will  be  seen  that  if  an  alternating  current  is  transmitted  to  a  dis- 
tance the  nearer  the  line  wires  to  each  other  the  smaller  the  self- 
induction  developed  in  them. 

In  an  alternating  current  circuit  the  self-induction  developed  in 
every  portion  is  not  the  same,  and  the  total  effect  is  equal  to  the 
sum  of  the  several  effects.  For  example  in  Fig.  21  let  A  A  A 
represent  a  circuit  that  is  fed  by  a  generator  at  G.  The  self- 


836 


HANDBOOK   ON    ENGINEERING, 


induction  on  the  line  A  will  be  small,  specially  if  the  wires 
are  placed  near  each  other.  If  a  number  of  incandes- 
cent lamps  are  connected  at  C  the  self-induction  of  these 
will  be  practically  nothing.  If  at  B  we  place  some  kind  of 
device  that  is  provided  with  wire  in  the  form  of  coils,  then  at  this 
point  a  large  self-induction  will  be  developed,  for  then  the 
magnetic  flux  from  each  turn  of  wire  in  the  coil  will  be  able  to  cut 


Jl 


through  many  other  turns,  and  thus  greatly  increase  the  inductive 
action.  To  determine  the  total  amount  of  inductive  action  in 
this  circuit,  so  as  to  ascertain  the  amount  of  current  that 
will  flow  through  it,  we  will  have  to  find  the  total  impedance 
of  the  circuit,  and  this  we  do  by  finding  the  impedance  of  each 
part  and  then  adding  these  impedances,  but  all  this  operation  is 
carried  out  not  in  the  way  in  which  we  add  figures,  but  in  the 
manner  shown  in  Fig.  10.  The  diagram  Fig.  22  illustrates  the 
operation.  By  actual  measurement  we  can  find  the  resistance  of 
the  line  A  in  ohms  and  we  can  mark  it  down  on  the  diagram  as 
o  a.  By  calculation,  we  find  the  reactance  of  line  A  and  mark  it 
down  as  a  a',  thus  we  obtain  the  impedance  of  o  a'  of  the  line. 
Next,  we  find  the  resistance  of  the  lamps  C  which  we  mark  down 
at  a'  6,  and  from  b  draw  b  b'  equal  to  the  reactance  of  the  lamps, 
thus  obtaining  the  impedance  a'  &',  of  the  lamps.  We  now  draw 
b'  c. equal  to  the  resistance  of  B  and  c  c'  equal  to  the  reactance  of 


HANDBOOK   ON    ENGINEERING.  837 

B  and  thereby  obtain  the  impedance  b'  c'  of  B.     We  now  join  o 


-"b 


B 


with  c'  and  obtain  the  line  C  which  is  the  total  impedance  of  the 
circuit,  and  line  B,  which  is  the  total  reactance,  while  line  A  is 
the  total  resistance.  A  glance  at  the  diagram  will  show  that  the 
total  impedance  C  is  less  than  the  sum  o  a!  a'  b'  and  b'  c'  if  these 
were  added  in  the  ordinary  way,  so  that  the  total  impedance  of  a 
circuit  can  be  less  than  the  direct  'sum  of  the  impedances  of  its 
several  parts. 


Fig.23 

The  angle  of  lag  between  the  current  and  impressed  e.m.f. 
in  an  alternating  circuit  plays  a  very  important  part  in  determin- 
ing the  actual  amount  of  energy  that  is  transmitted.  In  a 
continuous  current  circuit  the  energy  is  always  equal  to  the 


838 


HANDBOOK    ON    ENGINEERING. 


product  of  the  volts  by  the  amperes  but  in  an  alternating  circuit 
it  may  be  equal  to  this  product  and  it  may  not  be  as  much 
as  one  per  cent  of  this  product.  What  proportion  of  the  product 
of  the  volts  by  the  amperes  will  represent  the  actual  energy  trans- 
mitted will  .depend  upon  the  angle  of  lag  between  the  current 
and  the  impressed  e.m.f.,  the  greater  this  angle  the  less  the  en- 
ergy. The  way  in  which  the  angle  of  lag  affects  the  amount  of 
energy  flowing  in  the  circuit  can  be  made  clear  by  means  of  Figs. 
23  to  25.  In  these  figures,  curve  A  represents  the  impressed 
e.m.f.  and  curve  B  is  the  current,  while  the  shaded  curves  repre- 
sent the  energy.  In  Fig.  23  the  impressed  e.m.f.  and  the  current 


are  shown  in  phase  with  each  other,  and  as  a  result  the  curves  C 
which  represent  the  energy  are  drawn  above  line  0  T,  thus  show- 
ing that  all  the  energy  is  positive,  and  it  is  equal  to  the  direct 
product  of  the  volts  by  the  amperes.  In  Fig.  24  the  current  and 
impressed  e.m.f.  are  drawn  out  of  phase  90  degrees.  Starting 
from  0,  the  e.m.f.  is  positive  while  the  current  is  negative,  curve 
B  being  below  line  0  T.  This  means  that  the  current  and  e.m.f. 
act  against  each  other  hence  the  energy  represented  is  negative. 
After  the  first  quarter  of  a  period,  the  current  becomes  positive 


HANDBOOK    ON    ENGINEERING. 


839 


and  then  the  energy  is  positive.  Thus  for  the  first  half  period  we 
heave  two  energy  curves,  D  negative,  and  C  positive,  both  of  these 
are  equal  and,  therefore,  just  offset  each  other,  so  that  the  net 
energy  flowing  in  the  circuit  during  this  time  is  zero.  As  will  be 
seen,  during  the  following  half  periods,  the  same  operation  is  re- 
peated, so  that  the  actual  result  is  that  energy  is  putinto  the  circuit 
during  one  quarter  period,  and  during  the  next  quarter  it  is  taken 


Fig.25 


out,  and  the  actual  energy  flowing  through  the  circuit  is  nothing. 
The  action  is  the  same  as  when  a  swing  is  set  in  motion,  during 
the  first  half  of  each  swing  energy  is  accumulated  by  the  descent 
of  the  weight,  but  during  the  next  half  it  is  all  absorbed  in  lifting 
the  same  weight,  and  unless  we  supply  from  outside  enough  en- 
ergy to  overcome  the  friction  the  swing  will  soon  come  to  a 
standstill.  In  an  alternating  current  circuit,  if  the  impressed 
e.m.f.  and  the  current  were  out  of  phase  90  degrees  no  energy 
would  be  introduced  into  the  circuit,  hence,  no  current  at  all 
could  flow,  but  if  the  angle  is  a  trifle  less  than  90,  say  89,  a  suf- 
ficient amount  of  energy  can  be  put  into  the  circuit  to  overcome 
the  resistance  loss,  and  then  a  strong  current  will  sway  back  and 
forth  that  is  not  capable  of  doing  any  work.  A  current  of  this 


840  HANDBOOK    ON    ENGINEERING. 

kind  is  called  a  wattless  current  as  it  carries  no  energy.  The  rea- 
son why  it  carries  no  energy  is  that  the  self-induction  very  nearly 
balances  the  impressed  e.m.f.  so  that  the  effective  e.m.f.  is  very 
small,  in  fact  it  is  just  enough  to  force  the  current  against  the 
resistance  of  the  circuit. 

In  Fig*  25  the  current  and  imprissed  e.m.f.  are  shown  out  of 
phase  by  an  angle  of  45  degrees,  and  as  will  be  seen  the  shaded 
curves  G  which  represent  positive  energy,  are  much  larger  than 
those  below  line  0  T,  which  represent  negative  energy.  The 
difference  between  these  two  is  the  actual  energy  flowing  in  the 
circuit.  It  can  be  clearly  seen  that  the  smaller  the  angle  of  lag 
between  the  current  and  impressed  e.m.f.  the  larger  the  shaded 
curves  above  line  0  T  and  the  smaller  those  below  the  line ; 
hence,  the  greater  the  energy  flowing  in  the  circuit. 

By  the  use  of  condensers,  the  effect  of  self-induction  can  be 
counteracted,  and  in"  that  way  the  lag  of  the  current  can  be  re- 
duced and  thus  the  energy  in  the  circuit  can  be  increased.  A 
condenser  is  a  device  that  is  so  constructed  as  to  be  able  to  re- 
ceive a  very  large  electriostatic  charge.  To  explain  the  nature 
of  electrostatic  charges  so  that  they  may  be  understood  we  may 
say  that  bodies  arranged  so  as  to  hold  a  charge  will  carry  this 
charge  upon  their  surface.  Thus  we  can  picture  to  the  mind's 
eye  the  charge  as  flowing  over  the  surface  until  it  completely 
covers  it.  When  a  condenser  is  used  in  an  alternating  current 
circuit,  it  is  charged  and  discharged  each  time  the  current 
alternates,  and  the  time  relation  of  the  charging  and  discharging 
currents  is  such  as  to  be  directly  opposite  to  the  current  that  would 
flow  under  the  effect  of  the  self-induction,  or,  to  put  it  in  another 
way,  the  e.m.f  of  the  condenser  current  is  180  degrees  -out  of 
phase  writh  the  self-induction.  Now,  by  properly  proportioning 
the  condenser  it  can  be  made  to  just  balance  the  self-induction, 
and  then  we  get  the  relations  illustrated  in  Fig.  26  in  which  curve  B 
represents  the  self-induction,  curve  C  the  condenser  e.m.f.  which 


HANDBOOK    ON    ENGINEERING. 


841 


is  directly  opposite  and  of  equal  magnitude.  Curve  A  represents 
the  impressed  e.m.f .  as  well  as  the  current,  both  being  in  phase 
with  each  other. 

The  general  principle  of  construction  of  a  condenser  is  illus- 
trated in  Fig.  27,  in  which  the  plates  A  B  represent  the  condenser, 


and   G  the  generator  that  provides  the  current,  the    connecting 
wires  being  S  S.     A  device  of  this  kind,  if  placed  in  a  continuous 


B 


Fig.27 

current  circuit,  will  simply  prevent  the  ilow  of  current ;  but  when 
connected  in  an  alternating  current  circuit,  if  of  the  proper  pro- 
portions, will  act  as  if  it  did  not  break  the  circuit.  This  is  because 


842  HANDBOOK    ON    ENGINEERING. 

the  large  surfaces  on  the  plates  A  B  act  as  reservoirs  and  accumu- 
late all  the  current  that  flows  into  them  during  the  short  time  each 
impulse  lasts.  When  the  current  reverses,  the  charge  in  the  con- 
denser runs  out  together  with  the  generator  current.  We 
can  thus  consider  that  if  a  positive  impulse  of  the  current  fills 
plate  A  and  empties  plate  B,  a  negative  impulse  will  reverse  the 
operation. 

Mutual  induction*  —  In  connection  with  Fig.  2  it  was  shown 
that  when  an  alternating  current  flows  through  a  wire,  the  alter- 


Fig.28 

nating  magnetic  flux  that  surrounds  the  wire,  if  it  cuts  through 
any  other  wires  running  parallel  with  it  will  induce  e.m.fs.  in 
them.  The  direction  and  phase  of  these  e.m.fs.  will  be  the  same 
as  that  of  the  self-induction  in  the  wire  carrying  the  current.  If 
we  have  two  wires  running  parallel  with  each  other  and  alternat- 
ing currents  flow  through,  then  the  action  of  wire  No.  1  upon 
wire  No.  2  will  be  the  same  as  that  of  No.  2  upon  No.  1.  This 
action  is  called  mutual  induction,  and  it  is  made  use  of  in  the 


HANDBOOK    ON    ENGINEERING. 


843 


construction  of  an  apparatus    used  for  transforming  alternating 
currents  which  is  commonly  called  a  transformer. 

By  the  aid  of  Fig.  28  the  principles  of  mutual  induction  can  be 
made  quite  clear.  In  this  diagram  suppose  that  the  circle  A  rep- 
resents one  wire  through  which  an  alternating  current  is  flowing, 
and  circle  B  represents  another  wire  carrying  an  alternating  cur- 
rent. If  these  two  wires  are  some  distance  apart,  it  is  clear  that 
a  considerable  portion  of  the  magnetic  flux  of  A  will  not  cut 
through  B,  and  in  like  manner  that  a  considerable  portion  of 
the  flux  of  B  will  not  cut  though  A,  as  is  indicated  by 


Fig.29 


the  dotted  circles  at  a  a  a.  In  any  case,  however,  some 
of  the  flux  of  one  wire  will  cut  through  the  other.  From 
this  it  follows  that  the  effect  of  the  current  in  each  wire 
upon  the  other  wire  will  be  less  than  that  upon  itself, 
but  the  closer  the  wires  are  to  each  other  the  nearer  equal 
the  effects  will  be.  When  it  is  desired  to  avoid  the  effects  of 
mutual  induction  as  far  as  possible  the  wires  must  be  separated 
to  the  greatest  distance,  and  when  we  desire  to  make  the  mutual 
inductive  effect  the  greatest,  we  must  bring  the  wires  as  close 


844  HANDBOOK    ON    ENGINEERING. 

together  as  possible.  The  inductive  effect  of  wires  upon  each 
other  in  some  cases  produces  very  objectionable  results,  for 
example  when  telephone  wires  are  run  side  by  side  for  any 
distance  the  inductive  action  of  one  wire  upon  the  other  serves 
to  render  the  conversation  indistinct.  Why  this  is  so  it  can  be 
appreciated  at  once  from  an  inspection  of  Fig.  29,  which  shows 
a  pole  carrying  four  wires.  Telephone  currents  are  not  alter- 
nating but  they  pulsate  and  thus  produce  the  same  effect  as  if 
they  were  alternating.  In  Fig.  29  the  circles  drawn  around 
each  one  of  the  wires  as  will  be  seen  cut  through  all  the  other 
wires.  If  the  two  upper  wires  belong  to  one  circuit  and  the  two 
lower  ones  to  another,  then  if  one  set  of  wires  are  crossed  at  every 
three  or  four  poles  so  that  the  wire  running  on  the  right  side 
for  a  certain  distance  will  then  be  changed  over  to  the  left  side, 
the  inductive  actions  will  be  counteracted  to  a  very  great  extent 
and  this  method  is  followed  in  stringing  telephone  wires.  It  is 
also  used  in  regular  alternating  current  circuits  when  interference 
between  different  circuits  is  to  be  avoided. 

With  regards  to  the  two  wires  belonging  to  the  same 
circuit,  it  is  advantageous  to  string  them  as  close  together  as 
possible,  for  in  this  case,  the  effect  of  mutual  induction  is  to 
neutralize  the  effect  of  self-induction.  Referring  to  Fig.  20  it 
can  be  seen  at  once  that  if  the  magnetic  flux  at  (7  develops  a  self- 
induction  in  lower  A  toward  the  right,  it  will  develop  an  induc- 
tion in  upper  A  also  towards  the  right,  but  with  reference  to  the 
wire  itself  this  induction  will  be  just  opposite  to  that  in  the  lower 
side  so  that  the  two  will  counteract  each  other.  Thus  to  reduce 
the  reactance  of  the  line,  the  two  sides  of  the  circuit  must  be 
placed  as  near  together  as  is  practicable. 

Transformers*  —  A  transformer  is  an  apparatus  in  which  the 
principle  of  mutual  induction  is  utilized  for  the  purpose  of  gener- 
ating a  second  current  by  the  inductive  action  of  a  primary 
current.  Referring  to  Fig.  28  it  can  be  seen  that  if  wire  B  is 


HANDBOOK    ON    ENGINEERING. 


845 


closed  upon  itself  the  e.m.f.  induced  in  it  by  the  magnetic  flux 
issuing  from  A  will  cause  a  current  to  flow  and  then  this  current, 
which  is  brought  into  existence  by  the  inductive  action  of  the 
current  in  A,  will  in  turn  develop  a  magnetic  flux  that  will  react 
upon  wire  A  in  precisely  the  same  manner  as  if  the  current  were 
not  induced  in  J5,  but  it  came  from  an  independent  source.  In  a 
transformer,  the  wire  is  wound  in  the  form  of  compact  coils,  and 
one  of  these  coils,  which  is  called  the  primary,  is  connected  with 
an  alternating  current  circuit.  The  current  flowing  through  this 
coil  induces  a  current  in  the  other  coil  which  is  called  the  second- 
ary. The  general  construction  of  a  transformer  can  be  under- 


,,c^Vf 

I    '    ^r^      V  .  \ 


M- 


'/C 


Fig.30 


stood  from  Fig.  30.  An  iron  core  C  is  provided  upon  which  are 
wound  two  coils  marked  A  and  B.  The  coil  A  which  is  the  prim- 
ary, is  connected  with  an  alternating  current  circuit,  and  thus  the 
iron  core  C  is  strongly  magnetized.  The  presence  of  the  iron  core 
C  serves  to  greatly  increase  the  magnetic  flux  but  does  not  in  any 
way  interfere  with  its  alternating  properties,  so  that  it  increases 
and  decreases  and  changes  its  direction  in  precisely  the  same 
manner  as  the  flux  that  surrounds  a  single  wire.  The  flux  de- 


846  HANDBOOK    ON    ENGINEERING. 

veloped  by  A,  swells  out  as  indicated  by  the  lines  a  a  a  and  cuts 
through  the  .side  of  the  secondary  coil  B.  If  the  circuit  through 
this  coil  is  close  an  alternating  current  will  be  generated  in  it, 
and  this  current  will  develop  a  magnetic  flux  that  will  swell  out 
and  cut  the  side  of  the  primary  coil  A.  The  e.m.f.  induced  in 
A  by  the  flux  of  B  will  be  in  opposition  to  the  self-induction  de- 
veloped by  its  own  flux,  hence,  if  the  circuit  through  B  is  open, 
the  current  flowing  through  A  will  be  small  because  the  self- 
induction  will  counteract  the  impressed  e  m.f.  so  as  to  leave  but 
a  small  effective  e.m.f.  As  soon  as  the  circuit  through  B  is 
closed,  the  inductive  action  of  this  coil  upon  A  will  offset  to  a 
certain  extent  the  self-induction  and  thus  assist  the  impressed 
e.m.f  .in  forcing  more  current  through  A.  The  more  the  current 
through  B  is  increased,  the  stronger  its  action  upon  A  and  as  a 
result  the  more  the  self-induction  of  A  will  be  neutralized  and  the 
stronger  the  primary  current  will  become.  This  action  which 
occurs  in  a  perfectly  natural  manner  serves  to  make  the  trans- 
former a  self-regulating  apparatus,  so  that  if  a  strong  current  is 
required  in  the  secondary  circuit,  a  strong  current  passes  through 
the  primary  so  as  to  furnish  the  energy  necessary  to  develop  the 
strong  secondary  current.  If  no  current  is  drawn  from  the 
secondary,  the  primary  current  is  reduced  to  nearly  nothing. 

To  explain  fully  the  action  in  a  transformer  would  require  a 
rather  lengthy  discussion  of  the  principles  involved,  but  the 
action,  in  a  general  way,  can  be  made  clear  without  going  deeply 
into  the  theory.  In  explaining  the  phase  relation  of  the  current 
the  self-induction  and  the  impressed  e.m.fs.  in  connection  with 
Fig.  8  it  was  shown  that  the  angle  between  the  self-induction  and 
the  current  is  90  degrees,  and  that  the  angle  between  the  current 
and  the  impressed  e.m.f,  can  be  anything  from  zero  up  to  nearly 
90  degrees.  If  the  current  is  passed  through  transformers  or 
other  iDductivc  devices,  the  current  will  lag  considerably 
Suppose  U  lags  10  degrees  then  the  total  angle  between  the  un- 


HANDBOOK    ON    ENGINEERING.  847 

pressed  e.m.f.  and  the  self-induction  will  be  100  degrees.  Now 
in  a  transformer  the  e.m.f.  induced  in  the  secondary  coil  is  in 
phase  with  the  self-induction  in  the  primary  coil,  hence,  with  the 
above  angles  it  would  be  100  degrees  behind  the  impressed  e.m.f. 
in  the  primary  coil.  Now  if  the  secondary  current  lags  as  much 
as  the  primary,  it  will  be  110  degrees  behind  the  primary  im- 
pressed e.m.f.  and  the  magnetic  flux  developed  by  this  current 
will  induce  an  e.m.f.  in  the  primary  coil  90  degrees  behind 
itself  or  200  degrees  behind  the  primary  impressed  e.m.f. 
This  e.m.f.  induced  in  the  primary  coil  by  the  action  of  the  sec- 
ondary current  not  only  counteracts  the  self-induction  in  the 
primary  coil,  but  in  addition  changes  the  phase  relation  between 
the  primary  current  and  its  impressed  e.m.f.,  making  the  angle 
smaller.  This  change  in  the  phase  relation  between  the  current 
and  impressed  e.m.f.  results,  in  turn,  in  a  change  of  the  phase 
relation  of  the  secondary  current,  and  this  change  in  the  phase  of 
the  secondary  makes  a  corresponding  change  in  the  phase  of  the 
primary.  If  we  were  to  trace  up  the  action  back  and  forth  from 
primary  to  secondary  currents  we  would  finally  arrive  at 
the  true  phase  relation  of  the  currents  and  e.m.fs.  inboth  circuits 
but  this  is  a  complicated  and  unnecessary  process  of  reasoning. 
We  can  easily  see  that  the  current  induced  in  the  secondary  coil 
will  have  a  certain  phase  relation  with  respect  to  the  primary 
current,  and  we  can  further  see  that  the  combined  magnetizing 
effect  of  the  two  currents,  the  primary  and  secondary,  is  the 
same  as  that  of  a  single  current  having  a  phase  intermediate 
between  the  phases  of  these  two.  Following  this  course  of 
reasoning  we  have  only  one  inductive  action  to  deal  with  and  this 
is  in  such  a  phase  relation  that  as  it  increases  it  decreases  the  self- 
inductive  e.m.f.  in  the  primary  and  thus  permits  more  current  to 
pass  through  this  coil,  and  this  increase  in  current  in  the  primary 
causes  a  corresponding  increase  in  the  secondary  current.  When 
the  secondary  current  is  very  small  the  self-induction  in  the 


848  HANDBOOK    ON    ENGINEERING. 

primary  is  very  great  and  as  a  result  the  lag  of  the  primary 
current  is  increased  and  its  strength  is  decreased.  As  the  sec- 
ondary current  ^increases,  the  self-induction  in  the  primary 
decreases,  and  the  lag  of  the  primary  current  reduces  while 
the  current  strength  increases.  The  strength  of  the  secondary 
current  is  varied  by  varying  the  resistance  in  the  secondary 
circuit ;  if  this  resistance  is  reduced  the  current  is  increased. 

To  make  a  transformer  as  perfect  as  possible  it  is  necessary  to 
place  the  primary  and  secondary  coils  in  such  a  position  that 
the  mutual  induction  between  them  may  be  the  greatest  pos- 
sible, that  is  so  that  all  the  magnetic  flux  developed  by 
the  primary  coil  may  cut  through  the  secondary  and  all 
the  flux  of  the  secondary  may  cut  through  the  primary. 
If  the  coils  are  arranged  as  in  Fig.  30  it  can  be  seen  at  once  that 
all  the  flux  of  A  will  not  cut  through  B  and  in  like  manner  all  the 
flux  of  B  will  not  cut'  thro  ugh  A.  It  is  not  possible  to  arrange 
the  coils  so  that  all  the  flux  of  one  coil  will  pass  through  all  the 
turns  of  wire  on  the  other  coil,  but  this  condition  can  be  very 
nearly  realized.  If  one-half  of  coil  A  is  wound  on  each  side  of 
the  core  G  and  then  the  B  coil  is  wound  in  two  parts  directly 
over  the  A  coils  the  chance  for  the  flux  of  one  coil  to  not  pass 
through  the  other  coil  will  be  greatly  reduced. 

The  flux  that  does  not  pass  through  the  opposite  coil  is  called  a 
leakage  flux,  thus  in  Fig.  30  the  lines  a  that  pass  through  coil 
A  but  not  through  B  constitute  the  leakage  from  coil  A  and  in 
like  manner  the  flux  of  coil  B  that  does  not  pass  through  A  is 
the  leakage  of  B.  The  leakage  flux  represents  just  so  much  mag- 
netism thrown  away,  hence  the  effort  of  the  designer  is  to  arrange 
the  coils  so  as  to  reduce  it  to  the  smallest  amount  possible.  If 
the  two  coils  were  wound  together,  that  is,  if  we  took  the  wires 
and  wound  them  side  by  side  forming  a  single  coil,  the  leakage 
would  be  practically  nothing,  but  this  construction  cannot  be  used 
as  with  it  .there  would  be  great  danger  of  the  insulation  between 


HANDBOOK    ON    ENGINEERING. 


849 


the  coils  giving  away,  and  this  would  destroy  the  transformer. 
This  form  of  winding  can  be  approximated  to  by  winding  each 
coil  in  many  sections  and  placing  these  in  sandwich  fashion  upon 


the  iron  core  as  is  shown  in  Fig.  31  in  which  the  sections  forming 
one  coil  are  shaded,  and  those  of  the  other  coil  are  not.  This  is 
the  construction  that  is  followed  generally  in  large  transformers. 
In  the  majority  of  designs,  however,  the  primary  and  secondary 
coils  are  wound  one  over  the  other. 

Transformers  are  used  for  the  purpose  of  changing  the  voltage 
of  the  current.  The  name  transformer  is  misleading,  as  it  creates 
the  impression  that  the  device  transforms  the  current,  when  as 
shown  in  the  foregoing  it  does  nothing  of  the  kind,  it  simply 
generates  a  secondary  current  which  is  in  no  way  connected  with 
the  primary.  When  electric  energy  is  transmitted  to  a  consider- 
able distance  by  means  of  alternating  currents,  the  voltage  used 
is  much  higher  than  is  required  for  the  operation  of  lamps 
or  motors,  hence,  at  the  receiving  end  of  the  line  this  cur- 
rent is  passed  through  transformers  and  secondary  currents  are 
generated  in  these  that  are  of  the  voltage  desired.  The  voltage 

54 


850  HANDBOOK    ON    ENGINEERING. 

of  the  secondary  current  is  controlled  by  the  number  of  turns  of 
wire  placed  upon  the  secondary  coils.  Roughly  speaking,  if 
the  primary  coil  has  ten  times  as  many  turns  as  the  secondary 
the  voltage  of  the  secondary  current  will  be  one-tenth  of  that  of 
the  primary.  If  the  primary  voltage  is  2000  and  the  secondary 
is  100  the  primary  coil  will  have  twenty  times  as  many  turns  of 
wire  as  the  secondary. 

Transformers  that  deliver  a  secondary  current  of  lower  volt- 
age than  the  primary  are  called  lowering  transformers,  while 
those  that  deliver  a  secondary  of  higher  voltage  are  called  raising 
transformers.  For  distributing  current  to  consumers,  lowering 
transformers  are  used.  But  in  long  distance  transmission  plants, 
where  the  current  in  the  transmission  line  has  ane.m.f.  of  any- 
where from  10,000  to  30,000  volts,  raising  transformers  are 
used  at  the  power  house,  and  these  take  the  current  from  the 
generators,  which  may  be  of  1,000  or  2,000  volts  and  deliver  to 
the  line  a  secondary  current  of  10,000  or  more  volts. 

Transformers  cannot  be  used  with  continuous  currents  for  the 
simple  reason  that  as  these  currents  do  not  fluctuate  the  magnetic 
flux  developed  by  them  remains  stationary  and,  therefore,  there 
is  no  inductive  action. 

A  medium  size  transformer  is  shown  in  Fig.  32.  The  com- 
plete transformer  is  seen  at  the  right  side  of  the  illustration.  In 
the  center  is  shown  the  lower  part  of  the  iron  core,  with  the  wire 
removed  from  one  leg,  this  wire  being  shown  on  the  left.  The 
iron  plates  at  the  bottom  of  the  figure  form  the  upper  part  of  the 
iron  core. 

The  iron  core  of  a  transformer  is  built  up  out  of  sheet  iron. 
It  could  not  be  made  a  solid  mass,  for,  if  it  were,  secondary  cur- 
rents would  be  induced  in  it,  and  thus  the  energy  in  the  primary 
current  would  be  used  up  in  developing  useless  currents  with  iron 
core.  The  sheet  iron  laminations  are  insulated  from  each  other, 
so  as  to  prevent  the  development  of  currents  in  the  core. 


HANDBOOK    ON    ENGINEERING. 


851 


As  can  be  seen  from  the  illustration  the  wire  wound  on  each 
leg  of  the  core  belongs  in  part  to  the  primary  and  in  part  to  the 
secondary  circuit.  If  the  primary  wire  is  proportioned  so  that  it 
is  proper  for^a  1,000  volt  current  when  the  parts  on  the  two  legs 
are  connected  in  series,  then  it  can  be  made  proper  for  500  volts 


Fig.  32. 

by  connecting  the  two  parts  in  parallel.  If  the  secondary  coils 
will  develop  a  voltage  of  100  when  both  parts  are  connected  in 
series,  they  will  develop  50  volts  if  both  parts  are  connected  in 
parallel,  but  in  this  case  the  current  will  be  doubled. 

The  transformer  as  shown  to  the  right  in  Fig.  32,  is  complete, 
but  for  the  purpose  of  protecting  the  wire  an  outer  casing  is  pro 


852  HANDBOOK    ON    ENGINEERING. 

yided.  For  high  voltage  transformers,  this  casing  is  made  water 
tight  and  is  filled  with  oil  so  as  to  improve  the  insulation  of  the 
apparatus.  Very  large  transformers  are  provided  with  means  for 
cooling  them.  In  some,  air  is  forced  through  the  coils  and  iron 
core.  In  others,  coils  of  pipe  are  placed  within  the  casing  and 
water  circulates  through  these. 

Alternating1  current  generators.  In  alternating  current  gen- 
erators the  field  is  magnetized  permanently  by  means  of  a  con- 
tinuous current.  This  current  is  obtained,  generally,  from  a  small 
continuous  current  generator  that  is  called  an  exciter.  Some  alter- 
nators as  a  rule  of  small  capacity  are  provided  with  a  commu- 
tator to  rectify  a  portion  of  the  current  the  machine  generates  so 
as  to  provide  a  continuous  current  to  magnetize  the  field.  An 
alternating  current  cannot  be  used  to  magnetize  the  field  because 
the  field  magnetism  must  remain  unchanged. 

Alternators  are  also  arranged  so  that  the  field  is  magnetized 
by  the  combined  action  of  the  two  continuous  currents  above 
mentioned,  that  is,  by  the  current  from  a  separate  exciter  and 
the  current  derived  from  the  armature.  Alternators  excited  in 
this  manner  are  called  compound  machines  and  are  the  counter- 
part of  the  continuous  current  generator.  Alternators  that  are 
excited  by  the  current  from  a  separate  exciter  alone  are  the  coun- 
terpart of  the  plain  shunt  wound  continuous  current  generator. 

There  are  several  other  ways  in  which  the  field  can  be  magnet- 
ized to  make  an  alternator  of  the  compound  type,  and  the  most 
important  of  these  will  be  found  fully  explained  under  the  head- 
ing of  "Compensated  Generators." 

The  object  of  compound  winding  in  alternators  is  the  same  as 
in  continuous  current  generators,  that  is,  to  keep  the  voltage  con- 
stant and  not  allow  it  to  drop  as  the  current  strength  increases. 
Large  alternators  used  in  central  stations  are  always  of  the  com- 
pound type. 

The  way  in  which  alternating  current  generators  act  can  be 


HANDBOOK   ON   ENGINEERING. 


853 


understood  from  the  diagrams  Figs.  33  to  37.  In  Fig.  33  P 
and  N  represent  the  poles  of  the  field  magnet  of  a  two-pole 
machine.  The  armtaure  is  provided  with  a  single  coil  of  wire 
marked  a.  When  this  coil  is  in  the  position  shown,  no  e.m.f. 
will  be  induced  in  it,  but  as  it  begins  to  rotate  from  this  position 
an  e.m.f.  will  begin  to  be  induced,  and  this  will  increase  in  mag- 
nitude until  one  quarter  of  a  revolution  has  been  made,  when  it 
will  be  at  the  maximum  value.  During  the  next  quarter  revolu- 
tion the  e.m.f.  will  gradually  reduce,  becoming  zero  when  the 
half  turn  is  completed.  During  the  next  half  turn  the  e.m.f.  will 
again  rise  to  a  maximum  and  fall  to  zero,  but  it  will  be  oppositely 


H 


Fig.  33. 


Fig.  34, 


Fig  35. 


directed,  so  that  if  during  the  first  half  turn  the  e.m.f.  is  posi- 
tive, during  the  next  half  it  will  be  negative,  and  this  operation 
will  be  repeated  for  each  revolution  of  the  armature.  Thus  it 
will  be  seen  that  if  the  armature  revolves  ten  times  in  a  second, 
the  frequency  of  the  current  generated  will  be  ten,  and  in  any 
case  the  frequency  will  be  equal  to  the  number  of  revolutions  the 
armature  makes  in  a  second.  This  is  true  for  a  two-pole  machine, 
if  the  generator  has  four  poles  the  frequency  of  the  current  will 
be  equal  to  twice  the  number  of  revolutions  per  second  and  for 
any  greater  number  of  poles  the  frequency  will  be  equal  to  the 
number  of  revolutions  of  the  armature  per  second  multiplied  by 
half  the  number  of  poles.  Alternating  current  generators  are 
always  made  with  a  large  number  of  poles  so  that  the  frequency 
required  may  be  obtained  without  running  the  armature  at  too 
great  a  speed. 


854  HANDBOOK    ON    ENGINEERING. 

The  diagram  Fig.  33  illustrates  a  simple  alternating  current 
generator,  or  what  is  called  a  single-phase  generator.  A  single- 
phase  machine  is  one  that  has  one  coil  on  the  armature  for  each 
pair  of  poles  in  the  fields  and  generates  one  alternating  current. 

Fig.  34  illustrates  diagrammatically  a  two-phase  generator.  A 
two-phase  generator  is  an  alternating  current  generator  that  gene- 
rates two  alternating  currents  that  are  out  of  phase  with  each 
other  by1  one-quarter  of  a  period,  that  is,  by  90  degrees.  Such  a 
generator  is  provided  with  two  coils  or  sets  of  coils  for  each  pair 
of  poles  and  these  are  placed  at  right  angles  to  each  other  in  a 
two-pole  machine  and  so  that  the  sides  of  one  set  come  opposite 
the  centers  of  the  other  set,  in  multi polar  machines. 

In  Fig..  34  it  will  be  seen  that  coil  a  is  in  the  same  position  as 
the  coil  in  Fig.  33,  hence  no  e.m.f.  is  being  induced  in  it.  Coil 
&,  however,  is  in  the  position  in  which  the  induced  e.m.f.  is  of  the 
maximum  value,  thus  it  will  be  seen  that  as  the  armature  revolves 
the  e.m.f.  in  one  coil  will  rise  toward  the  maximum  while  that  in 
the  other  coil  will  be  decreasing  toward  zero. 

Fig.  35  illustrates  a  three-phase  generator.  A  three-phase 
generator  is  a  machine  that  generates  three  alternating  currents 
that  are  out  of  phase  with  each  other  by  an  angle  of  120  de- 
grees, or  one-third  of  a  period.  Such  a  machine  has  three  coils 
or  sets  of  coils  for  each  pair  of  field  poles. 

In  Fig.  35  it  will  be  seen  that  coil  a  is  in  the  position  in  which 
no  e.m.f.  is  generated,  and  if  we  assume  that  the  armature  is  re- 
volving in  the  direction  of  the  hands  of  a  clock,  then  the 
e.m.f.  induced  in  coil  b  is  very  near  the  maximum  value,  but  is 
still  increasing,  and  will  become  the  maximum  when  the  coil 
reaches  the  horizontal  position.  In  coil  c  the  e.m.f.  has  passed 
the  maximum  and  is  reducing  toward  zero,  which  value  it  will 
reach  when  the  coil  reaches  the  vertical  position,  or  the  position 
in  which  a  now  is. 

If  an  alternator  is  of  the  multipolar  type  the  coils  will  be  dis- 


HANDBOOK    OJST    ENGINEERING. 


855 


posed  in  the  manner  shown  in  Fig.  36.  If  it  is  a  single-phase 
machine  it  will  have  one  set  of  coils  only,  those  marked  A.  If  it 
is  a  two-phase  generator  it  will  have  two  sets  of  coils,  the  addi- 


Fig.  36. 


tional  set  being  placed  in  the  position  snown  in  broken  lines  and 
marked  B.  In  this  construction  the  machine  appears  to  have  as 
many  A  coils  as  there  are  poles  and  the  same  number  of  B  coils, 
which  is  in  contradiction  to  the  statement  made  above,  that  a  single- 
phase  machine  has  one  coil  for  each  pair  of  poles.  The  truth, 


however,  is  that  each  coil  in  Fig.  36  is  virtually  one-half  of  a 
coil.  Fig.  37  shows  the  way  in  which  the  coils  are  arranged  in  a 
three-phase  generator  of  the  multipolar  type,  the  three  sets  of 
coils  being  marked  ABC.  In  monocyclic  generators  the  coils 


856 


HANDBOOK    ON    ENGINEERING. 


are  arranged  as  in  Fig.  36,  but  they  differ  from  the  two-phase 
winding  in  that  the  B  coils  are  one-quarter  the  size  of  the  A  coils. 
In  actual  generators  the  armature  coils  are  seldom  given  the  form 
shown  in  these  diagrams,  but  whatever  the  form  may  be  the  prin- 
ciple of  winding  is  the  same. 

In  an  alternator  the  armature  coils  forming  one  set  are  connected 
in  series  with  each  other,  and  the  entering  end  of  the  first  coil  and 
the  leaving  end  of  the  last  coil  are  connected  with  collector  rings 
mounted  upon  the  armature  shaft,  and  the  current  is  taken  from 
these  by  means  of  brushes  similar  to  the  commutator  brushes  of 


Fig.  38. 

continuous  current  machines.  In  monocyclic  generators  one  end 
of  the  B  set  of  coils  is  connected  with  the  middle  point  of  the 
A  set,  and  the  three  remaining  ends  are  connected  with  col- 
lector rings.  This  is  the  arrangement  with  generators  of 
what  is  known  as  the  revolving  armature  type,  which  is  the 


HANDBOOK    ON    ENGINEERING.  857 

one  illustrated  in  Fig.  33  to  37.  There  is  another  type  in 
which  the  outer  part  which  is  stationary  is  the  armature  and  the 
revolving  part  is  the  field.  Machines  of  this  kind  are  called  re- 
volving field  alternators.  The  principle  of  operation  is  the  same 
in  both  types,  but  the  revolving  field  type  has  the  advantage  that 
as  the  armature  is  stationary,  no  collector  rings  and  brushes  are 
required  to  take  off  the  current.  All  that  is  necessary  is  to  pro- 
vide binding  posts  to  which-  the  ends  of  the  armature  coils  are  con- 
nected, and  from  these  the  external  circuit  wires  are  run  off. 

A  revolving  field  alternator  is  shown  in  Fig.  38.  In  machines 
of  this  type,  the  field  magnetizing  coils  are  mounted  on  the 
periphery  of  the  revolving  part,  hence  the  current  that  traverses 
them  must  pass  through  collector  rings  mounted  upon  the  shaft. 
These  rings  are  clearly  shown  in  the  illustration,  the  collector 
brushes  being  held,  insulated  from  each  other,  by  the  stand 
located  in  front  of  the  rings.  Thus  it  will  be  seen  that  this  type 
of  machine  requires  collector  rings,  just  the  same  as  the  revolving 
armature  type,  but  the  difference  between  the  two  is  that  in  the 
latter  the  whole  armature  current  passes  through  the  collector 
rings,  and  on  that  account  they  must  be  made  very  large,  while 
in  the  revolving  field  machines  they  can  be  made  small,  as  only  the 
field  current  passes  through  them,  and  this  is  only  from  one  to 
two  per  cent  of  the  armature  current. 

There  is  still  another  type  of  alternating  current  generator  in 
which  the  wire  on  the  field  as  well  as  the  armature  is  held  station- 
ary. Such  machines  are  called  inductor  generators.  The  revolv- 
ing portion  of  such  generators  is  simply  a  mass  of  iron  formed 
like  a  very  large  pinion  with  correspondingly  large  teeth.  When 
this  part  revolves  the  ends  of  the  teeth  sweep  over  the  armature 
coils,  running  as  close  to  them  as  they  can  without  touching.  The 
magnetic  flux  developed  by  the  field  coil  issues  from  the  ends  of 
the  teeth  and  cuts  through  the  armature  coils  thus  inducing  e.m.fs. 
in  them.  It  will  be  seen  that  the  difference  between  this  type  of 


858 


HANDBOOK    ON    ENGINEERING. 


generators  and  the  revolving  armature  type  is  that  instead  of  re- 
volving the  armature  coils  through  the  stationary  field  flux,  the 
latter  is  revolved  and  the  armature  coils  are  held  stationary.  The 


\ 


Fig.  39. 


difference  between  the  inductor  generator  and  the  revolving  field 
type  is  that  in  the  latter  the  field  is  magnetized  by  a  number  of 
coils  and  these  are  rotated  together  with  the  field  poles,  while  in 
the  inductor  machine  there  is  a  single  field  magnetizing  coil  and 
this  remains  stationary,  the  part  that  revolves  being  what  might 
be  called  the  poles. 

An   inductor   alternator    is   shown   in  Fig.    39.     The    small 
machine  mounted  on  the  right  side  of  the  base  is  the  exciter  that 


HANDBOOK    ON    ENGINEERING.  859 

furnishes  the  field  magnetizing  current.  The  outer  casing  of  the 
machine  holds  a  ring  built  up  of  sheet  iron  laminations,  which 
constitutes  the  armature  and  supports  the  armature  coils.  The 
large  teeth,  or  polar  projections  which  are  well  shown  in  the 
illustration  are  carried  by  the  revolving  part,  and  when  rotating 
cause  the  magnetic  flux  to  sweep  over  the  armature  coils.  The 
field  coil  is  placed  back  of  these  polar  projections. 

Alternating  current  generators  are  run  singly,  or  they  may  be 
connected  in  parallel,  but  they  cannot  be  run  in  series.  If  an 
attempt  is  made  to  run  them  in  series,  one  of  the  machines  will 
act  as  a  motor  and  will  be  driven  by  the  current  generated  by  the 
other.  When  alternators  are  connected  in  parallel  it  is  necessary 
that  they  run  at  exactly  the  same  velocity,  if  they  are  identical 
in  construction.  If  the  generators  are  not  of  the  same  construe-* 
tion  then  their  velocities  will  depend  upon  the  number  of  poles 
each  one  has.  Machines  of  different  size  and  even  design,  can  be 
connected  in  parallel,  providing  the  frequency  of  the  currents 
they  generate  are  the  same.  To  make  the  frequency  the  same  it 
is  necessary  that  the  velocity  of  each  machine  multiplied  by  the 
number  of  poles  it  has  be  equal  to  the  same  number.  Thus  if 
one  machine  has  twice  as  many  poles  as  the  other,  it  must  run  at 
one-half  the  velocity.  The  velocity  of  alternators  connected  in 
parallel  must  be  equal,  absolutely,  and  not  practically  so  ;  that 
is,  if  two  machines  are  alike,  and  one  runs  at  1000  revolutions 
per  minute,  the  other  must  run  at  1000  and  it  cannot  run  at  999 
or  1001.  Since  such  extreme  accuracy  in  speed  is  necessary  it 
might  be  inferred  that  it  is  practically  impossible  to  run  alter- 
nators in  parallel  unless  their  shafts  are  coupled  together,  or  they 
are  connected  through  spur  gearing  with  the  same  driving  shaft. 
As  a  matter  of  fact,  however,  alternators  can  be  run  in  parallel 
even  if  one  is  driven  by  a  steam  engine  and  the  other  by  a  water 
wheel,  and  they  may  be  side  by  side  or  several  miles  apart.  The 
reason  why  this  is  the  case  is  that  when  the  machines  are  in  oper- 


860  HANDBOOK    ON    ENGINEERING. 

ation,  the  current  holds  them  in  step.  If  several  generators  are 
feeding  into  the  same  circuit,  and  one  machine  tends  to  lag 
behind  the  others,  its  current  reduces  and  thus  the  speed  in- 
creases as  less  power  is  required  to  drive  it.  If  the  tendency  to 
lag  increases,  the  machine  begins  to  act  as  a  motor,  and  is  driven 
by  the  current  from  the  other  machines. 

While  it  is  possible  to  run  alternators  in  parallel  under  almost 
any  conditions  providing  they  are  speeded  so  as  to  generate  cur- 
rents of  the  same  frequency  and  nearly  the  same  voltage,  entirely 
satisfactory  results  cannot  be  obtained  unless  the  angular  motion 
is  uniform,  that  is,  unless  the  velocity  of  rotation  is  the  same  at 
all  points  of  the  revolution.  If  a  steam  engine  has  a  light  fly- 
wheel the  velocity  of  the  shaft  will  not  be  the  same  at  all 
points  of  the  revolution,  but  will  be  the  slowest  when  the 
crank  is  passing  the- center,  and  the  fastest  when  at  half  stroke. 
This  fact  is  clearly  shown  by  the  irregular  motion  of  the 
paddle-wheels  of  river  boats  driven  by  a  single  engine. 

If  two  alternators  are  driven  by  two  engines  whose  rotative 
motion  is  not  uniform  and  the  engines  are  so  timed  that  one 
is  on  the  center  when  the  other  is  at  half -stroke,  then  the 
action  of  the  two  alternators  will  be  irregular,  for  when  one 
machine  is  rotating  at  the  highest  velocity  the  other  will  be  ro- 
tating at  the  lowest.  This  uneven  action  of  the  alternators  may 
be  compared  with  the  work  of  two  horses  hitched  to  a  wagon  and 
pulling  unevenly.  If  both  horses  pull  together  all  the  time  the 
whiffle-tree  will  remain  straight  and  the  wagon  will  be  drawn 
along  smoothly ;  but  as  soon  as  the  horses  begin  to  pull  unevenly 
the  whiffle-tree  will  be  jerked  back  and  forth  and  the  motion  of 
the  wagon  will  be  irregular.  In  this  case  the  horses  soon  tire 
out  because  they  work  against  each  other  part  of  the  time.  The 
action  between  two  alternators  that  do  not  rotate  with  uniform 
velocities  is  practically  the  same  as  that  of  two  horses  that  do 
not  work  together ;  the  machine  that  runs  ahead  not  only  sends  a 


HANDBOOK    ON    ENGINEERING.  861 

current  into  the  main  circuit,  but  in  addition  backs  up  a  cur- 
rent through  the  other  generator,  thus  wasting  energy  by 
causing  a  strong  current  to  flow  back  and  forth  between  the  two 
machines.  To  overcome  this  difficulty  engines  made  to  drive 
alternators  are  provided  with  extra  heavy  flv  wheels,  so  that  the 
momentum  may  be  sufficient  to  keep  the  speed  up  to  the  normal 
point  while  the  crank  is  passing  the  center. 

With  small  alternators  that  have  only  a  few  poles  and  are 
driven  by  high-speed  engines,  the  effect  of  irregular  motion  is  not 
so  great  as  in  large  machines  having  many  poles,  hence  the  large 
slow-speed  engines  used  to  drive  alternators  having  a  large  num- 
ber of  poles,  must  be  provided  with  excessively  large  flywheels  to 
run  in  a  satisfactory  manner. 

The  reason  why  alternators  with  a  large  number  of  poles  require 
greater  regularity  in  motion  to  give  satisfactory  results,  can  be 
easily  understood.  Suppose  we  have  a  pair  of  two-pole  machines 
driven  by  engines  whose  flywheels  are  25  ft.  in  circumference. 
Suppose,  further,  that  the  irregularity  in  motion  is  such  that  each 
engine  when  running  at  the  faster  velocity,  gets  three  inches  ahead 
of  the  other.  Then  the  advance  in  position  will  be  one  per  cent, 
and  consequently  the  currents  of  the  two  generators  will  run 
ahead  and  behind  each  other  one  per  cent  at  each  quarter  of  a 
revolution.  Now,  if  these  same  two  engines  drive  two  twenty- 
pole  alternators,  then  the  irregularity  in  motion  will  be  multiplied 
ten  times,  because  one-tenth  of  a  revolution  will  give  one  cycle  of 
current,  and  the  current  of  each  machine  will  run  ahead  and  fall 
behind  the  other  ten  per  cent,  instead  of  one  per  cent.  • 

Starting  alternators  connected  in  parallel :  —  In  starting  con- 
tinuous current  generators  that  are  connected  in  parallel  all  we 
have  to  do  is  to  set  one  machine  in  operation  and  then  after  the 
second  one  is  running  up  to  full  speed,  we  adjust  its  field  regu- 
lator until  the  voltage  is  the  same  as  that  of  the  first  machine,  or 
one  or  two  volts  higher.  .  We  then  throw  the  switch  and  connect 


862  HANDBOOK    ON    ENGINEERING. 

it  with  the  switchboard.  In  starting  alternators  that  are  con- 
nected in  parallel  we  have  to  do  more  than  this,  we  must  not  only 
adjust  the  second  machine  so  that  its  voltage  is  the  same  as  that 
of  the  first,  but  we  must  bring  it  up  to  the  proper  speed  and  get  its 
current  in  phase  with  that  of  the  first  generator  before  we  connect 
it  with  the  switchboard.  To  accomplish  all  this  with  certainty, 
devices  are  used  that  are  called  synchronizers,  or  phase  indicators. 
These  devices  consist  generally  of  a  couple  of  small  transformers 
one  of  which  is  connected  with  the  circuit  of  each  generator.  The 
secondary  wires  of  these  transformers  are  connected  with  each 
other  and  one  or  two  incandescent  lamps  are  connected  in  this 
circuit.  When  the  second  machine  is  started  up,  as  its  speed  is 
much  lower  than  that  of  the  generator  already  in  operation  the 
frequency  of  the  secondary  current  of  its  transformer  will  be  much 
lower  than  that  of  the  first  machine,  and  as  a  result  the  lamps  in 
the  circuit  of  the  two  transformers  will  flicker  rapidly.  As  the 
second  machine  builds  up  its  speed  the  flickering  of  the  lamps 
will  become  slower.  When  the  two  generators  are  running  at 
nearly  the  same  speed  the  flickering  will  be  replaced  by  rather 
long  periods  of  darkness  and  light.  During  the  periods  when  the 
lamps  are  lighted  the  current  generated  by  one  of  the  transformers 
is  in  such  a  direction  as  to  act  in  series  with  the  current  of  the 
other  and  thus  draw  the  current  through  the  lamp.  When  the 
lamps  are  dark  it  is  because  the  currents  of  the  two  transformers 
are  in  opposition  to  each  other  and  thus  no  current  passes  through 
the  lamps.  The  second  generator  is  connected  with  the  switch- 
board during  one  of  the  periods  of  darkness  or  brightness,  de- 
pending upon  the  way  in  which  the  transformers  are  connected. 
The  second  generator  will  not  be  running  at  exactly  the  proper 
speed  when  it  is  connected  with  the  switchboard,  but  as  soon  as 
it  is  connected  the  currents  of  the  two  machines  acting  upon  each 
other  will  at  once  draw  the  second  machine  into  step  with  the 
first  one,  and  they  will  continue  to  run  in  step  even  if  the  power 


HANDBOOK    ON    ENGINEERING. 


863 


driving  one  of  the  machines  should  fail.  In  the  latter  case,  the 
first  machine  would  not  only  furnish  current  for  the  main  cir- 
cuit, but  would  in  addition  drive  the  second  machine  as  a  motor. 
The  way  in  which  synchronizing  lamps  are  connected  in  single 
or  polyphase  circuits  is  clearly  illustrated  in  the  diagram  Fig.  40. 

To  Bus  Bars. 


Synchronizing 

lvP: M/WVf 


•ansfbrmers 
on 


Tempor  wry 


TPS.TSwiCch. 
a       OP 


76  Generator. 
Fig.  40. 

The  three  upper  lines  are  connected  with  the  main  bus-bars  on 
the  switchboard  and  the  lower  lines  run  to  the  generator  that  is  to 
be  synchronized.  The  left  side  of  the  diagram  shows  the  connec- 
tions for  synchronizing  a  single-phase  generator.  In  such  a  case, 
the  middle  wire  running  to  the  bus-bars  and  to  the  generator  would 
not  be  used.  The  synchronizing  transformers  would  have  their 
primary  coils  connected  with  the  side  wires  in  the  manner  shown 
by  lines //and  g  g.  When  the  generator  current  is  in  synchro- 
nism with  that  in  the  bus-bars,  the  primary  currents  in  the  two 
synchronizing  transformers  will  flow  in  the  direction  of  the  arrows 
a  a,  and  the  secondary  currents  will  be  in  the  direction  of  arrows 
c,  that  is,  in  opposition  to  each  other,  so  that  no  current  will  pass 
through  the  synchronizing  lamps.  If  the  connections  of  one  of 


864  HANDBOOK    ON    ENGINEERING. 

the  transformers  are  reversed,  either  in  the  primary  or  secondary, 
the  two  secondary  currents  will  flow  through  the  lamps  in  the  same 
direction  as  indicated  by  the  arrows  d  on  the  right  side  of  the 
diagram.  Thus  it  will  be  seen  that  the  synchronizing  lamps  can 
be  arranged  so  that  they  will  light  up  when  the  generator  current 
is  in  phase  with  the  bus-bar  current,  or  they  may  be  arranged  so 
as  to  be  dark  at  this  instant.  Generally  they  are  arranged  so  as 
to  be  bright  when  the  current  is  in  phase  and  the  switch  connect- 
ing the  generator  with  the  switchboard  is  closed  at  the  instant 
when  the  lamps  appear  to  be  brighter. 

When  two  and  three-phase  generators  are  started  up  the  first 
time  a  temporar}^  synchronizing  arrangement  is  connected  in  the 
manner  shown  on  the  right  side  of  Fig.  40.  The  synchronizing 
lamps  on  the  left  side  will  show  that  the  current  flowing  in  the 
two  side  wires  is  in  synchronism,  but  this  does  not  show  that 
the  other  currents  also  synchronize.  To  make  sure  that  the 
temporary  transformer  is  properly  connected  the  connections  e 
are  made  first,  and  if  the  lamps  on  both  sides  of  the  diagram 
become  dark  and  bright  together,  the  connections  are  correct. 
The  connections  are  then  broken  and  are  transferred  to  the  middle 
wire  ;  then  when  all  the  currents  are  synchronized,  all  the  lights 
will  light  up  together.  Generally  the  internal  connections  of 
synchronizing  transformers  are  properly  made,  and  the  correct 
connection  of  the  terminal  wires  is  clearly  indicated  so  that  mis- 
takes in  making  connections  are  not  very  liable. 

Compensating  and  compounding  alternators. —  Continuous 
current  generators  are  provided  with  a  compound  field  winding 
for  the  purpose  of  maintaining  the  voltage  uniform  as  the  arma- 
ture current  increases.  Alternating  current  generators  are 
compounded  for  the  same  purpose.  If  the  field  of  an  alternator 
is  excited  by  a  current  derived  from  an  exciter  the  voltage  of 
the  machine  will  drop  as  the  strength  of  the  current  generated  in 
the  armature  increases.  A  part  of  the  drop  is  due  to  the  fact 


HANDBOOK    ON    ENGINEERING.  865 

that  the  increased  current  absorbs  more  voltage  in  passing  through 
the  armature  coils.  The  balance  of  the  drop  is  produced  by 
the  reaction  of  the  armature  current  upon  the  field.  As  the 
current  of  the  exciter  that  magnetizes  the  field  remains  constant, 
the  magnetization  produced  by  it  remains  constant.  The  cur- 
rent flowing  in  the  aternator  armature  acts  to  demagnetize  the 
field,  and,  as  its  action  increases  as  the  strength  increases  it 
follows  that  the  stronger  the  current  becomes  the  weaker  the 
field  will  be,  and,  as  a  result,  the  lower  the  voltage  of  the  cur- 
rent generated  in  the  alternator  armature. 

If  a  portion  of  the  current  of  the  alternator  armature  is  recti- 
fied by  being  passed  through  a  commutator  and  is  used  to  assist 
the  exciter  current  to  magnetize  the  field  then  the  field  magnetism 
will  increase  as  the  armature  current  increases,  because  the 
action  of  the  rectified  current  will  increase.  Thus  by  the  com- 
pound action  of  the  exciter  current  and  the  rectified  armature 
current,  the  magnetism  of  the  field  of  the  alternator  can  be  made 
to  increase  as  the  armature  current  increases,  and  in  this  way  the 
voltage  is  increased  so  as  to  compensate  for  the  greater  drop  of 
voltage  on  the  armature  coils,  the  result  being  that  the  voltage 
impressed  upon  the  wire  remains  practically  the  same  for  all 
strengths  of  current. 

The  above  results  can  be  obtained  providing  the  phase  relation 
between  the  current  and  the  impressed,  or  line  e.m.f.  does  not 
change ;  but  if  the  phase  relation  is  continually  changing  such 
perfect  regulation  cannot  be  realized.  The  reason  why  changes 
in  the  phase  of  the  current  interfere  with  the  regulation  is  that 
the  same  strength  of  armature  current  will  produce  different  de- 
grees of  reaction  on  the  field  magnetism  with  different  phase 
relations.  If  the  lag  of  the  current  is  increased  the  reaction  upon 
the  field  will  be  increased,  and  in  like  manner  a  decrease  in  the 
lag  will  reduce  the  reaction  upon  the  field.  Several  arrangements 
are  used  for  obtaining  field  magnetizing  currents  that  will  com- 

55 


866  HANDBOOK    ON    ENGINEERING. 

pensate  for  variations  in  the  lag  of  the  current  as  well  as  for  va- 
riations in  strength.  Alternators  provided  with  such  arrange- 
ments are  called  "  Compensated  Generators."  The  way  in  which 
a  field  magnetizing  current  is  obtained  that  will  compensate  for 
variations  in  lag  as  well  as  in  current  strength  is  by  using  a  por- 
tion of  the  armature  current  to  vary  the  strength  of  the  current 
generated  by  an  exciter,  the  exciter  being  provided  with  coils 
through  which  the  current  taken  from  the  armature  is  passed. 
These  coils  are  so  disposed  that  their  governing  action  upon  the 
exciter  is  proportional  to  the  lag  of  the  current  as  well  as  its 
strength,  hence  the  current  that  the  exciter  sends  through  the 
field  coils  of  the  alternator  is  at  all  times  sufficient  to  compensate 
for  variations  in  the  strength  and  phase  of  the  armature  current. 

If  an  alternator  is  single-phase,  one  commutator  is  sufficient  to 
rectify  the  portion  of  .the  armature  current  and  to  magnetize  the 
field.  For  a  two-phase  machine,  two  commutators  are  required 
and  for  a  three-phase,  three  commutators.  To  obviate  using 
two  and  three  commutators  in  polyphase  generators,  trans- 
formers are  employed,  two  transformers  for  two-phase  and 
three  transformers  for  three-phase.  The  recording  currents 
of  these  transformers  are  combined  into  one,  and  this  com- 
bined current  is  passed  through  a  single  commutator  to  be  recti- 
fied. In  some  cases  only  one  of  the  currents  of  a  two  or  three- 
phase  generator  is  rectified,  but  with  most  machines,  if  they  are 
connected  in  parallel,  care  must  be  taken  to  have  the  circuits 
from  which  the  rectified  current  is  taken  properly  connected  with 
each  other ;  if  not,  one  armature  will  short  circuit  the  other. 
This  is  due  to  the  fact  that  when  alternators  are  run  in  parallel 
the  rectified  currents  for  the  field  coils  are  connected  with  each 
other  through  equalizer  wires,  in  a  manner  similar  to  that  used 
with  continuous  current  generators. 

The  ordinary  connections  for  two  generators  in  parallel  are 
shown  in  the  diagram  Fig.  41. 


HANDBOOK    ON    ENGINEERING. 


867 


As  will  be  seen,  the  field-magetizing  currents  derived  from  the 
commutators  are  connected  with  each  other  through  the  equalizer 
switches,  hence,  to  avoid  short  circuiting  the  armature  through  the 
equalizer  connections,  if  the  commutator  rectify  one  current  only, 


CONNECTIONS  OF  COMPOSITE  FIELD  ALTERNATING  GENERATORS 

FOR  RUNNING  IN  MULTIPLE 


Synchr0o.r;r.g  Plug 


Fig.   41. 

the  two  rectified  currents  must  be  in  phase  with  each  other.  The 
rheostats  shown  in  each  field  circuit  are  for  the  purpose  of 
adjusting  the  voltage  of  each  generator  independently. 

The  use  of  transformers  to  transform  the  portion  of  the  arma- 
ture current  that  is  rectified  is  no  objection  against  polyphase 
machines,  because,  even  with  single  phases,  the  armature  voltage 
is  generally  so  high  that  a  transformer  is  used  so  as  to  obtain  a 
secondary  current  of  low  voltage  to  pass  through  the  field  coils. 

Alternating  Current  Motors* — From  the  foregoing  it  can  be 
understood  that  an  alternating  current  generator  can  be  used  as 
a  motor  providing  it  is  supplied  with  the  same  kind  of  currents, 


868  HANDBOOK    ON    ENGINEERING. 

that  is,  with  a  continuous  current  to  magnetize  the  field,  and  with 
an  alternating  current  for  the  armature.  A  single-phase  alter- 
nator will  run  as  a  motor  if  connected  in  a  single-phase  circuit. 
Two-phase  generators  will  act  as  two-phase  motors,  and  three- 
phase  generators  will  act  as  three-phase  motors.  With  either  one 
of  these  three  types  of  machines  a  continuous  current  will 
be  required  to  magnetize  the  field.  Two  and  three-phase  ma- 
chines can  be  run  with  a  single  alternating  current,  by  connect- 
ing one  of  the  armature  circuits  only,  or  all  the  circuits  may  be 
used  if  they  are  connected  in  parallel. 

When  an  alternator  is  used  as  a  motor  it  is  called  a  synchro- 
nous motor,  because  it  runs  in  synchronism  with  the  generator 
that  supplies  the  current.  A  simple  alternator  (single-phase  ma- 
chine) becomes  a  single-phase  synchronous  motor,  and  a  two 
or  three-phase  generator  becomes  a  two  or  three-phase  syn- 
chronous motor. 

A  single-phase  synchronous  motor  will  not  start  up  of  its  own 
accord,  but  must  be  set  in  motion  and  run  up  to  nearly  its  full 
speed  before  it  will  begin  to  act  as  a  motor.  If  it  is  started  up 
without  a  load  when  it  comes  rather  near  to  its  full  speed  it  will 
give  a  sudden  jump  and  swing  into  step  with  the  current  and  then 
continue  to  run  at  this  velocity.  If  it  is  started  with  a  full  load 
it  will  not  fall  into  step  with  the  current  until  its  speed  is  very 
nearly  up  to  the  proper  point.  Synchronous  motors  are  never 
started  under  load,  they  are  always  started  light. 

Two  and  three-phase  synchronous  motors  can  be  started  with- 
out outside  assistance.  Synchronous  motors  are  generally  pro- 
vided with  a  self-starting  motor,  to  set  them  in  motion,  or  else 
they  are  arranged  so  as  to  be  self -starting  by  being  converted, 
jn  the  act  of  starting,  into  some  form  of  motor  that  is  self- 
starting. 

Fig.  42  shows  a  synchronous  motor  of  large  size  provided 
with  an  induction  motor  of  much  smaller  capacity  to  start  it. 


HANDBOOK    ON    ENGINEERING. 


869 


This  motor  is  of  the  revolving  field  type,  and,  as  will   be  seen,  is 
precisely  the  same  as  the  same  type  of  generator. 


1000    H.     P.    TWO-PHASE     REVOLVING     FIELD    SYNCHRONOUS    MOTOR. 

Fig.  42." 

Owing  to  the  fact  that  synchronous  motors  are  not  self -starting, 
they  are  generally  used  only  where  large  power  is  required,  unless 
they  happen  to  be  made  so  as  to  be  self -starting,  then  they  are 
used  in  small  sizes. 

A  synchronous  motor,  when  running,  will  keep  in  step  with  the 
current,  no  matter  how  much  the  load  may  vary,  provided  it  is 
not  made  greater  than  the  capacity  of  the  machine.  If  the  load 
is  made  so  great  that  the  motor  cannot  carry  it,  the  armature 
will  be  pulled  out  of  step  with  the  current  and  will  imme- 
diately come  to  a  stop.  On  this  account,  motors  of  the 
synchronous  type  are  not  well  adapted  to  operate  cranes  or  similar 
machines  in  which  there  is  a  liability  of  greatly  overloading  the 
machine  occasionallv. 


870  HANDBOOK    OX    ENGINEERING. 

The  current  developed  by  an  alternating  current  generator  will 
lag  behind  the  impressed  e.m.f.  as  has  been  fully  explained  in  the 
foregoing.  If  this  curreutis  passed  through  a  second  machine,  that 
acts  as  a  motor,  the  latter  will  tend  to  generate  a  current  that  flows 
in  opposition  to  that  of  the  generator  ;  hence,  in  this  current  the  lag 
will  be  in  the  opposite  direction  of  that  of  the  current  that  drives 
it.  That  is  when  the  machine  acts  as  a  motor  its  whole  action  as 
a  generator  is  reversed.  Owing  to  this  fact,  if  a  synchronous 
motor  is  placed  at  one  end  of  a  circuit,  and  a  generator  at  the 
other,  the  motor  will  act  to  neutralize  the  self-induction  of  the 
generator,  and  thus  to  bring  the  current  in  the  circuit,  and  the 
impressed  e.m.f.  into  phase  with  each  other.  Thus,  a  synchro- 
nous motor  can  be  made  to  act  in  the  same  way  as  a  condenser, 
to  reduce  the  lag  of  the  current. 

Power  factor. —  In  an  alternating  current  circuit,  it  is  very 
important  to  reduce  the  lag  of  the  current  as  far  as  possible 
because  the  actual  amount  of  energy  carried  by  the  current  depends 
upon  the  angle  of  lag,  as  was  fully  explained  in  connection  with 
Figs.  23  to  25.  In  a  continuous  current  circuit  the  power  is 
always  equal  to  the  product  of  the  volts  by  the  amperes, 
but  in  an  alternating  current  circuit  this  product  is  not  a 
measure  of  the  power.  It  is  called  the  apparent  power,  or  the 
volt-amperes.  The  actual  power  is  equal  to  the  amperes  multi- 
plied by  the  e.m.f.  in  phase  with  the  current,  or  the  active  voltage, 
as  it  is  called.  The  ratio  between  the  true  power  and  the  volt- 
amperes  is  called  the  power  factor.  The  power  factor  can  be 
obtained  by  dividing  the  true  power  by  the  volt-amperes,  and  it 
may  range  from  100  per  cent  when  the  current  and  impressed 
e.m.f.  are  in  phase  down  to  five  or  ten  per  cent  when  the  angle  of 
lag  is  nearly  90  per  cent.  In  actual  working  circuits  the  power 
factor  ranges  between  about  95  and  75  per  cent.  Any  kind  of 
device  that  has  a  low  reactance,  as,  for  example,  incandescent 
lamps,  acts  to  keep  the  angle  of  lag  of  the  current  small,  and  thus 


HANDBOOK    ON    ENGINEERING.  871 

the  power  factor  high.  Devices  having  large  reactance,  such  as 
transformers,  and  induction  motors  act  to  increase  the  angle  of 
lag  of  the  current,  and  thus  to  reduce  the  power  factor.  Devices 
that  develop  a  negative  reactance,  that  is,  which  cause  the  current 
to  lead  the  impressed  e.m.f.,  such  as  condensers  and  synchronous 
motors,  can  be  used  in  circuits  in  which  transformers  and  similar 
devices  are  operated  so  as  to  counteract  these  and  thereby  keep 
up  the  percentage  of  the  power  factor. 

Induction  and  other  types  of  motors*  —  In  addition  to  the 
synchronous  motors  just  explained,  the  only  type  of  machine  that 
requires  notice  here  is  the  induction  motor.  This  is  by  far  the 
most  extensively  used  of  all  alternating  current  motors,  and  from 
the  manner  in  which  it  acts  it  has  a  greater  range  of  adaptability 
than  any  other  type.  It  may  be  well  to  mention  here,  however, 
that  a  plain  motor,  such  as  those  used  with  continuous  currents, 
can  be  made  to  operate  with  alternating  currents  providing  the 
field  cores  are  made  laminated,  instead  of  solid  castings.  If  the 
field  is  solid  the  motor  will  not  run  if  connected  in  an  alternating 
current  circuit  because  the  large  mass  of  iron  constituting  the  field 
cannot  be  magnetized  and  demagnetized  as  fast  as  the  current 
alternates.  If  we  take  hold  of  a  freight  car  and  try  to  shake  it 
we  will  fail  in  the  effort,  simply  because  the  bulk  is  too  great  to 
be  set  in  motion  rapidly.  If,  however,  we  take  hold  of  the  side 
of  a  light  buggy  and  shake  it  we  will  be  able  to  produce  a  very 
vigorous  movement,  simply  because  the  bulk  is  light.  In  the 
same  way,  if  we  attempt  to  alternate  the  magnetic  polarity  of 
large  masses  of  iron  \re  fail  because  the  bulk  is  too  great,  but  if 
v  e  divide  the  mass  up  lato  many  thin  sheets  we  will  have  no  diffi - 
cu'ty  in  causing  its  polarity  to  change  rapidly.  Alternating  cur- 
rent motors  of  this  kind  which  are  called  commutator  motors, 
hfeve  been  made,  but  they  are  not  used  or  manufactured  for  com- 
mercial purposes  at  the  present  time,  because  they  are  fur  inferior 
to  other  types.  They  are  open  to  two  objections,  one  of  which 


872 


HANDBOOK    ON    ENGINEERING. 


is  that  they  spark  considerably  and  the  other  is  that  they  will  not 
give  much  more  than  one-third  the  power  that  the  same  machine 
will  develop  if  supplied  with  a  continuous  current.  The  reason 
why  they  give  such  small  power  is  that  on  account  of  the  many 
turns  of  wire  on  the  field  the  inductive  action  is  very  great,  hence 
the  reactance  is  very  high,  and  as  a  result  the  current  lags  exces- 
sively so  that  the  power  factor  is  very  low,  therefore,  although  the 
current  is  strong,  the  actual  energy  carried  by  it  is  comparatively 
small.  Several  other  types  of  alternating  current  motors  have 
been  devised,  but  they  have  never  got  beyond  the  experimental 
stage. 

Principle  of  the  induction    motor- — Induction   motors  are 
made  for  single  and  polyphase  currents.     When  in  operation  the 


Fig.  43. 


Fig.  44. 


principle  of  action  is  the  same  in  all,  but  in  the  act  of  starting  the 
single-phase  machine  is  different  from  the  others.  Single-phase 
induction  motors  will  not  start  of  their  own  accord  unless  provided 
with  special  starting  arrangements.  The  most  common  way  of 
arranging  a  single-phase  induction  motor  so  as  to  be  self-starting 
is  to  provide  a  set  of  starting  coils  that  virtually  convert  it  into  a 


HANDBOOK    ON    ENGINEERING.  873 

two-phase  machine  in  the  act  of  starting.  When  the  motor  is 
under  way  the  starting  coils  are  cut  out,  although  in  some  cases 
they  are  left  in  circuit  all  the  time.  The  principle  of  the  induc- 
tion motor  can  be  explained  by  the  aid  of  the  diagrams  Figs. 
43  to  46.  These  diagrams  illustrate  the  action  in  a  two-phase 
machine  which  is  the  one  most  easily  understood.  The 
single-phase  induction  motor  is  the  most  difficult  one  to  ex- 
plain or  to  understand,  so  we  will  leave  it  for  the 
last.  In  an  induction  motor,  the  stationary  part,  which  is 
called  the  stator,  and  sometimes  the  field,  is  provided  with  coils 
that  are  connected  with  the  operating  circuits.  The  rotating  part 
which  is  called  the  rotor  and  sometimes  the  armature,  is  provided 
with  coils  that  are  short  circuited  upon  themselves  and  are  not 
connected  with  the  operating  circuits.  The  principle  of  operation 
generally  stated  is  that  the  currents  in  the  stator  develop  an  in- 
ductive action  upon  the  coils  of  the  rotor  thus  developing  currents 
in  these,  the  action  being  substantially  the  same  as  that  in  a 
transformer.  On  that  account  the  stator  is  also  called  the 
primary  member,  while  the  rotor  or  armature  is  commonly  called 
the  secondary  member.  The  primary  currents  passing  through 
the  coils  of  the  stator,  develop  a  magnetic  flux  and  the  secondary 
currents  induced  in  the  coils  of  the  rotor  also  develop  a  magnetic 
flux,  these  two  fluxes  are  at  an  angle  with  each  other,  and,  hence, 
there  is  a  strong  attraction  exerted  between  them,  the  magnetism 
of  the  rotor  making  an  effort  to  place  itself  parallel  with  that  of 
the  stator.  The  magnetism  of  the  stator  rotates,  on  account  of 
being  developed  by  alternating  currents,  and  the  magnetism  of 
the  rotor  in  trying  to  place  itself  parallel  with  that  of  the  stator 
also  rotates,  chasing  the  latter  around  the  circle  but  never 
overtaking  it. 

In  Fig.  43  let  A  A  represent  two  coils  connected  in  one  of  the 
circuits  of  a  two-phase  system,  and  let  B  B  represent  two  other 
coils  connected  in  the  other  circuit  of  this  same  system.  Suppose 


874 


HANDBOOK    ON    ENGINEERING. 


we  consider  the  instant  of  time  when  the  current  flowing  through 
the  A  A  coils  is  at  its  maximum  value,  then  at  this  very  same  instant 
the  current  in  the  B  B  coils  will  be  zero.  The  current  in  the  A  A 
coils  is  then  the  only  magnetizing  current  acting  upon  the  ring  at 
this  instant.  Suppose  the  direction  of  the  current  through  A  A 
is  such  as  to  develop  a  magnetic  flux  that  will  traverse  the  space 
in  the  center  of  the  ring  in  the  direction  of  arrow  C.  As  the 
current  in  the  A  A  coils  begins  to  decrease,  that  flowing  in  the 
B  B  coils  will  begin  to  increase.  Let  the  direction  of  the  current 
in  the  B  B  coils  be  such  as  to  send  a  magnetic  flux  through  the 
center  of  the  ring  in  the  direction  of  arrow  C  in  Fig.  45.  This 
magnetization  will  act  upon  that  developed  by  the  current  in  the 
A  A  coils  and  will  have  a  tendency  to  twist  it  around  into  the 
direction  of  arrow  C  in  Fig.  44.  When  the  current  in  the  A  A 
coils  has  reduced  and  the  current  in  the  B  B  coils  has  increased 
until  they  are  both  equal,  then  each  one  will  act  with  equal  force 


Fig.  46. 

to  establish  a  magnetization  in  its  own  direction ,  and  the  result 
will  be  that  the  actual  direction  of  the  magnetic  flux  will  be  as 
indicated  by  arrow  C  in  Fig.  44.  Thus  we  see  that  by  the 
decrease  in  the  strength  of  the  current  in  the  A  coils  and  the 


HANDBOOK    ON    ENGINEERING.  875 

increase  in  the  strength  of  the  current  in  the  B  B  coils  until  they 
are  both  equal,  the  magnetic  flux  has  been  rotated  from  the 
position  of  arrow  C  in  Fig.  43  to  its  position  in  Fig.  44.  Now 
as  the  variation  in  the  currents  progresses,  and  that  in  A  A 
becomes  weaker,  while  that  in  B  B  becomes  stronger,  the 
direction  of  the  magnetic  flux  will  be  still  further  rotated  so  that 
when  the  current  in  B  B  reaches  the  maximum  value,  and  that  in 
A  A  becomes  zero,  the  direction  of  the  flux  will  be  that  of  arrow 
C  in  Fig.  45.  As  we  advance  beyond  this  instant  of  time,  the 
current  in  B  B  will  begin  to  reduce,  while  that  in  A  A  will  begin 
to  increase,  but  its  direction  will  be  the  opposite  of  what  it  was 
in  Fig  43,  so  that  when  the  currents  in  the  two  sets  of  coils 
become  equal  again,  the  direction  of  the  magnetic  flux  will  be 
that  of  arrow  C  in  Fig.  46.  When  the  current  in  the  A  A  coils 
reaches  the  maximum  and  that  in  B  B  becomes  zero,  the  flux  will 
have  rotated  through  one-half  of  a  revolution  and  arrow  G  will 
be  in  the  vertical  position  but  pointing  downward. 

If  we  follow  the  action  of  the  currents  further  we  will  find  that 
as  a  result  of  the  continuous  increasing  and  decreasing  and 
changing  of  direction,  the  magnetic  flux  indicated  by  arrow  C 
will  continuously  rotate  keeping  time  with  the  frequency  of  the 
currents.  Now  if  we  suppose  that  an  armature  upon  which  a 
number  of  coils  are  wound  in  a  diametrical  position,  is  placed 
within  the  field  ring,  and  is  held  stationary,  we  will  see  at  once 
that  the  rotating  magnetic  flux  will  cut  through  its  coils  and 
develop  e.m.fs.  in  them.  The  currents  developed  in  these  coils 
on  the  stationary  armature  will  be  alternating,  hence,  they  will 
develop  a  magnetic  flux  in  the  armature  that  will  rotate,  and 
keep  time  with  the  rotating  flux  developed  by  the  field  coils. 
Both  these  fluxes  act  inductively  upon  the  field  and  armature 
coils,  their  combined  effect  being  equal  to  that  of  a  single  flux 
located  90  degrees  in  advance  of  the  e.m.f.  induced  in  the 
armature  coils,  hence,  somewhat  more  than  90  degrees  ahead  of 


876  HAND  BOOK    OX    ENGINEERING. 

the  armature  current.  If  we  hold  the  armature  by  means  of  a 
brake,  and  free  this  slightly,  so  that  the  armature  may  revolve 
slowly,  it  will  at  once  follow  around  after  the  rotating  field,  but 
as  its  magnetization  is  developed  by  currents  that  are  induced  by 
the  action  of  the  field  magnetism,  it  will  matter  little  how  fast 
the  armature  may  revolve,  its  magnetization  will  never  be  able  to 
overtake  that  of  the  field. 

As  can  be  judged  from  the  foregoing  explanation,  an  induction 
motor  is  not  a  synchronous  machine,  and  its  armature  can  never  at- 
tain a  velocity  equal  to  that  of  the  rotating  field.  If  the  resistance 
of  the  armature  coils  is  macte  very  low,  it  may  reach  a  velocity 
very  near  to  that  of  the  rotating  flux.  The  difference  between  the 
velocity  of  the  rotating  flux  and  that  of  the  rotating  armature  is 
called  the  slip  of  the  motor. 

If  the  motor  is  designed  for  constant  speed,  the  resistance  of 
the  armature- coils  is  made,  very  low,  and  then  when  the  machine  is 
running  free,  the  speed  of  the  armature  may  run  up  to  99  or  99 J 
per  cent  of  the  speed  of  the  rotating  field,  and  when  the  maximum 
load  is  put  on  it  may  not  drop  lower  than  94  or  95  per  cent.  If 
a  motor  is  designed  in  this  way  the  pull  of  the  armature  when  it 
starts  up  will  be  small  and  will  gradually  increase  until  the  speed 
is  about  nine-tenths  of  the  maximum  when  it  will  again  begin  to 
decrease. 

If  it  is  desired  to  make  a  motor  that  will  give  a  strong  pull 
when  it  starts  up,  its  armature  coils  must  have  more  resistance, 
and  then  it  will  pull  harder  on  the  start,  but  as  fast  as  the  speed 
builds  up  the  pull  will  reduce.  From  this  it  will  be  seen  that  in- 
duction motors  that  are  made  so  as  to  run  at  nearly  a  constant 
speed,  say  to  vary  five  or  six  per  cent  between  full  load  and  run- 
ning free,  will  not  give  a  strong  pull  in  the  act  of  starting,  hence 
they  will  have  to  be  started  without  a  load.  If  a  motor  is  to  be 
made  to  start  under  a  full  load  it  must  be  proportioned  so  that  it 
will  not  run  at  a  constant  speed,  but  will  gradually  reduce  its 
velocity  as  the  load  is  increased. 


HANDBOOK    ON    ENGINEERING.  877 

Induction  motors,  if  very  small,  are  started  by  connecting 
them  directly  with  the  operating  circuits,  but  if  they  are  of  any 
capacity  they  must  be  provided  with  some  kind  of  starting  resist- 
ance so  as  to  keep  the  starting  current  down  within  safe  limits. 
One  way  of  starting  is  to  introduce  resistance  into  the  primary 
circuits,  but  this  results  in  reducing  the  strength  of  the 
field,  and  thus  the  pull  of  the  armature.  Another  way  is  to  intro- 
duce resistance  into  the  armature  coil  circuit.  This  is  the  best 
method,  because  it  enables  the  motor  to  start  up  with  a  strong 
pull. 

Three-phase  induction  motors  act  in  precisely  the  same  way  as 
the  two-phase,  the  only  difference  being  that  the  rotation  of  the 
Held  flux  is  produced  by  the  increase  and  decrease  in  the  strength 
of  three  currents  flowing  through  three  sets  of  coils  equally 
spaced  around  the  circle  instead  of  by  the  increase  and  decrease 
in  two  currents  flowing  in  two  sets  of  coils  equally  spaced  around 
the  circle. 

In  the  single-phase  induction  motor,  the  magnetic  flux  developed 
by  the  single  alternating  current  traversing  a  single  set  of  coils  on 
the  field  combines  with  the  magnetic  flux  developed  by  the  armature 
current,  to  develop  a  rotatingfield  and  this  acting  upon  the  armature 
coils  produces  rotation  in  precisely  the  same  way  as  in  the  two- 
phase  machine.  This  is  the  action  that  takes  place  after  the 
armature  is  set  in  motion,  but  if  the  load  is  increased  and  the 
armature  speed  is  reduced  the  rotating  field  begins  to  become 
irregular,  and  by  the  time  the  armature  velocity  is  reduced  to 
about  one-half,  the  rotating  flux  becomes  so  irregular  in  its  move- 
ment, that  the  armature  pull  begins  to  reduce  very  rapidly,  and 
the  machine  comes  to  a  standstill.  Owing  to  this  fact  single- 
phase  induction  motors  cannot  be  used  in  cases  where  it  is  de- 
sired to  start  with  a  strong  pull,  or  where  a  wide  range  of  speed 
variation  is  desired. 

To  make  a  single-phase  induction  motor  self -starting,  it  is  wound 


878  HANDBOOK    ON    ENGINEERING. 

with  two  sets  of  coils,  like  the  diagrams  Figs.  43  to  4fi,  and  the 
current  from  the  single-phase  circuit  is  passed  through  these  two 
sets  of  coils  in  parallel  branches,  and  in  one  of  the  branches  the 
reactance  is  greatly  increased,  so  as  to  make  the  current  in  this 
branch  lag  much  more  than  in  the  other.  In  this  way  a  phase 
displacement  is  obtained  between  the  two  currents,  and  this  pro- 
duces a  corresponding  displacement  in  the  magnetic  fluxes  devel- 
oped by  the  two  sets  of  coils,  so  that  their  combined  action 
develops  a  rotating  field.  This  field  does  not  rotajte  at  a  uniform 
rate,  like  the  field  of  a  two-phase  motor,  but  it  is  uniform  enough 
for  the  purpose  of  setting  the  machine  in  motion.  To  increase 
the  reactance  in  th,e  auxiliary  starting  coils,  all  that  is  necessary 
is  to  wind  them  with  many  turns  of  fine  wire,  and  this  is  an 
arrangement  very  commonly  employed,  but,  in  some  cases,  sep- 
arate coils  are  placed  in  the  auxiliary  circuit  to  obtain  the  required 
reactance. 

There  are  other  ways  in  which  single-phase  induction  motors 
are  made  self -starting,  but  they  are  not  very  extensively  used. 

While  induction  motors  are  very  satisfactory  machines,  being 
adapted  to  every  kind  of  work,  even  to  the  operation  of  railway 
cars,  they  have  the  objection  of  being  highly  inductive  devices 
that  act  to  greatly  increase  the  lag  of  the  current,  and  thereby  to 
reduce  the  power  factor.  On  this  account  they  are  often  used  in 
connection  with  synchronous  motors  so  that  the  latter  may  coun- 
teract their  inductive  effect,  and  thus  keep  the  power  factor  high. 

The  small  motor  shown  in  Fig.  42,  is  an  induction  motor. 
Induction  motors  are  made  in  many  different  designs,  and  as 
large  as  300  to  400  H.  P.,  but  as  a  rule  they  are  confined  to  much 
smaller  capacities  ;  synchronous  motors  being  used  for  the  large* 
sizes. 

Rotary  transformers  and  rotary  converters*  —  A  rotary 
transformer  is  a  machine  by  means  of  which  a  continuous  current 
may  be  obtained  from  an  alternating  current.  A  rotary  con- 


HANDBOOK    ON    ENGINEERING. 


879 


verter  is  a  machine  for  accomplishing  the  same  result.  The 
essential  difference  between  the  two  is  that  the  first  is  driven  by 
an  alternating  current  and  generates  a  continuous  current,  while 
the  second  changes  an  alternating  into  a  continuous  current.  As 
a  result  of  this  difference  the  rotary  transformer  can  be  used  to 
obtain  a  continuous  current  of  any  desired  voltage  from  an 
alternating  current  of  any  given  voltage  ;  but  in  the  rotary  con- 
verter, as  the  action  is  to  convert  the  alternating  into  a  con- 
tinuous current,  the  voltage  relation  is  fixed  so  that  for  a  given 
alternating  current  voltage  we  will  get  a  corresponding  contin- 
uous current  voltage.  Both  these  machines  can  be  used  in  the 
reverse  order,  that  is  to  transform  or  convert  a  continuous  into  an 
alternating  current. 


B 


c    c 


Fig.   47. 

Principle  of  the  rotary  transformer* — The  principle  of  the 
rotary  transformer  is  illustrated  in  Fig.  47.  In  this  diagram  A 
represents  a  continuous  current  armature,  and  B  is  an  alternating 
current  armature.  If  both  these  are  provided  with  suitable 
magnetic  fields  then  if  continuous  current  is  passed  through  A  it 
will  become  a  motor  and  will  drive  B  and  generate  therein  a 
single  alternating  current  or  a  number  of  them  according  to  the 
way  in  which  the  armature  is  wound.  Thus  B  may  become  a 
single  or  a  polyphase  generator.  It  can  further  be  seen  that  the 


880 


HANDBOOK    ON    ENGINEERING. 


voltage  of  the  currents  generated  by  B  is  in  no  way  connected 
with  the  voltage  of  the  current  that  drives  A,  and  depends  wholly 
upon  the  way  in  which  B  is  wound.  If  B  is  connected  with  an 
alternating  current  circuit,  then  it  will  run  as  a  synchronous 
motor  and  drive  A  and  the  latter  will  generate  a  continuous 
current.  This  machine  if  driven  by  a  continuous  current  will  be 
self -starting,  but  if  driven  by  an  alternating  current  it  will  have 
to  be  started.  If  driven  by  an  alternating  current  its  speed  will 
be  controlled  by  the  frequency  of  the  current,  but  if  driven  by  a 
continuous  current  its  speed  will  vary  with  the  magnitude  of  the 
load  placed  upon  it. 


0 

n 

/ 

A 

C      ( 

u 

C 

y 

b 

\ 

J 

a  i 

Fig.  48. 

Fig.  49. 


Figs.  48  and  49  illustrate  the  principle  of  operation  and  the 
construction  of  a  rotary  converter.  The  armature  A  is  of  the 
continuous  current  type,  having  a  commutator  (7.  If  it  is  a  two- 
pole  machine,  then  if  wires  are  connected  with  diametrically 
opposite  segments  of  the  commutator  as  is  indicated  in  Fig.  49 
by  the  arrows,  and  these  are  connected  with  the  collector  rings 
a  a,  brtfshes  c  c  placed  on  these  rings,  will  take  of  a  true  alter- 
nating current  if  the  armature  is  placed  in  a  suitable  field  and  is 
driven.  While  alternating  current  can  be  taken  from  the  brushes 
c  c,  a  continuous  current  can  also  be  taken  from  the  brushes  b  b 


HANDBOOK    ON    ENGINEERING.  881 

which  bear  upon  the  commutator  C.  Thus,  this  machine,  if 
driven,  becomes  a  combination  generator  which  will  deliver  a 
continuous  and  an  alternating  current  at  the  same  time. 
Machines  of  this  type  are  constructed  and  are  called  double 
current  generators. 

If  the  brushes  c  c  are  connected  with  a  single-phase  circuit, 
and  the  armature  is  placed  in  a  suitable  field,  it  will  rotate  and 
from  the  b  b  brushes  of  the  commutator  a  continuous  current 
can  be  drawn.  If  the  brushes  b  b  are  connected  with  a  continu- 
ous current  circuit,  an  alternating  current  will  be  delivered 
through  the  brushes  c  c. 

If  four  wires  are  connected  with  four  commutator  segments  one 
quarter  of  the  circumference  apart,  and  these  are  connected  with 
four  collector  rings,  then  from  these  rings  two  alternating  cur- 
rents 90  degrees  out  of  phase  can  be  obtained.  Thus,  with  four 
connections  with  the  commutator  segments  the  machine  can 
convert  two  phase  currents  into  one  continuous  current,  or  one 
continuous  current  into  two  phase  currents,  thatis  into  two  alter- 
nating currents  90  degrees  out  of  phase. 

If  wires  are  connected  with  three  commutator  segments  one- 
third  of  the  circumference  apart,  and  these  are  connected  with 
three  collector  rings,  then  the  machine  will  become  a  three-phase 
converter,  and  if  connected  with  a  three-phase  system  will  deliver 
one  continuous  current  or  if  connected  with  a  continuous  current 
circuit  will  deliver  the  three  currents  of  a  three-phase  system. 

The  rotary  converter,  as  will  be  seen  from  the  foregoing, 
actually  changes  a  continuous  current  into  one  or  more  alternat- 
ing currents,  or  one  or  more  alternating  currents  into  one  con- 
tinuous current,  and  in  every  case  there  is  a  direct  electrical  con- 
nection between  the  continuous  and  the  alternating  current  cir- 
cuits. As  this  type  of  machine  simply  converts  the  current  of 
one  type  into  current  of  the  other  type  it  is  quite,  evident  that 
there  must  be  a  fixed  relation  between  the  strength  of  the  alternat- 

56 


882  HANDBOOK   ON    ENGINEERING. 

ing  and  continuous  currents  and  also  between  the  voltages.  An 
alternating  current  if  of  the  sine  type,  will  have  an  effective  value 
of  70.7  per  cent  of  its  maximum  value,  for  the  amperes  as  well  as 
the  volts.  So  that  if  we  have  a  continuous  current  of  70.7 
amperes  and  70.7  volts,  we  must  have  an  alternating  current  of 
100  amperes  maximum  value  and  100  volts  maximum  value  to  be 
equal  to  it,  and  if  the  energy  is  also  to  be  equal,  the  current  ia 
the  alternating  current  circuit  must  be  in  phase  with  it  e.m.f ., 
that  is  the  power  factor  must  be  100. 

In  a  rotary  converter  the  voltage  of  the  continuous  current  is 
equal  to  the  maximum  voltage  of  the  alternating  current  and  the 
strength  of  the  continuous  current  is  equal  to  one-half  the  maxi- 
mum strength  of  the  alternating  current.  Thus  if  the  maximum 
voltage  of  the  alternating  current  is  1,000  volts,  the  voltage  of  the 
continuous  current  will  be  1,000,  and  if  the  maximum  strength  of 
the  alternating  current  is  100  amperes  the  strength  of  the  contin- 
uous current  will  be  50  amperes.  This  arises  from  the  fact  that 
the  rotary  converter  does  not  develop  energy,  as  it  drives  itself, 
hence,  the  energy  in  the  continuous  current  cannot  be  more  than 
that  in  the  alternating,  in  fact  it  will  be  a  trifle  less  owing  to  the 
energy  absorbed  in  driving  the  machine.  Now  if  the  alternating 
e.m.f.  and  current  have  the  maximum  values  of  1,000  volts  and 
100  amperes,  their  effective  values  will  be  707  volts  and  70.7 
amperes,  and  the  product  of  these  two  will  be  the  energy  in  watts. 
Thus  707  X  70.7  =  50,000  watts.  Now  if  the  voltage  of  the 
continuous  current  is  1,000,  its  strength  must  be  50  amperes,  less 
the  amount  absorbed  in  overcoming  the  friction  of  the  machine. 

Fig.  50  shows  a  rotary  converter  of  large  size. 

Alternating  Current  Distributions*  —  The  principal  advantage 
of  alternating  over  continuous  currents  is  that  they  can  be  used 
for  transmitting  energy  to  much  greater  distances,  owing  to  the 
fact  that  a  high  voltage  can  be  used  to  transmit  the  main  current 
over  the  wire,  and  at  the  receiving  end  this  current  can  be  passed 


HANDBOOK    ON    ENGINEERING. 


883 


•through  transformers,  from  which  secondary  currents  of  low  volt- 
age may  be  obtained.     In  a  few  instances,  low  voltage  alternating 


ROTARY    CONVERTER. 

Fig.  50. 

currents  are  used  for  distributing  current  over  small  areas.  The 
general  arrangement  of  circuits  and  apparatus  for  a  three-phase 
system  of  this  kind  is  illustrated  in  the  diagram  Fig.  51. 


IB 


Fig.  51. 

The  generator  is  shown  at  the  extreme  left.  At  a  an  induction 
motor  is  connected  with  the  circuit.  At  b  an  "  arc"  light  is 
connected  in  the  secondary  circuit  of  a  small  transformer.  At  c 


884 


HANDBOOK    ON    ENGINEERING 


a  number  of  incandescent  lamps  are  connected.  At  d  the  circuit 
is  used  to  drive  a  rotary  transformer,  which  develops  a  continuous 
current  to  charge  storage  batteries  at  e.  The  three  solid  line 
wires  constitute  the  main  circuit  and  all  the  apparatus  is 
connected  with  them.  The  broken  line  above  these  is  the 
neutral  wire  and  is  connected  with  the  incandescent  lamps 
only.  If  the  number  of  these  lamps  in  each  circuit  is  the 
same,  as  is  shown  on  the  diagram,  no  current  will  pass  to  the 
neutral  wire,  but  if  in  one  of  the  circuits  there  are  more  lamps 
than  in  the  other,  the  excess  of  current  will  pass  to  or  from  the 
neutral  wire.  Systems  of  this  type  are  operated  at  voltages  rang- 
ing between  200  and  600. 


The  diagram,  Fig.  52,  shows  the  way  in  which  the  circuits  are 
arranged  when  the  distance  of  transmission  is  from  one  to  three 
or  four  miles,  For  such  cases,  the  voltage  generally  used  is 
2300.  The  generator  at  the  left  develops  currents  that  pass 
directly  to  the  main  line.  At  a  an  induction  motor  is  connected 
directly  to  the  main  line.  At  b  transformers  are  used  to  develop 
secondary  currents  of  low  voltage  to  supply  the  circuit  wjres  c 
from  which  the  motor  d  and  incandescent  lamps  e  are  fed.  At  f 
a  series  transformer  is  used  to  develop  a  secondary  current  o^ 
constant  strength  to  operate  the  arc  lamps  g.  The  difference  be- 
tween a  series  transformer  and  the  ordinary  type  is  that  the 
former  is  provided  with  a  mechanical  regulator,  actuated  by  the 
current  which  maintains  the  secondary  current  of  constant 
strength  and  varies  the  voltage  in  accordance  with  the  number  of 


HANDBOOK    ON    ENGINEERING. 


885 


lamps  in  service.  At  h  another  set  of  transformers  are  used  to 
develop  low  voltage  secondary  currents,  which  pass  through  a 
rotary  converter  i,  and  are  converted  into  a  continuous  current  to 
feed  the  incandescent  lamps  atj. 

The  diagram  53  illustrates  the  arrangement  of  circuits  and 
apparatus  for  long  distance  transmissions,  which  may  range  all 
the  way  from  five  or  six  miles  up  to  one  hundred  or  more,  the 
greatest  distance  covered  up  to  date  being  145  miles.  To  trans- 
mit current  to  great  distances  with  a  small  loss  in  the  trans- 
mission lines,  it  is  necessary  to  use  very  high  voltages,  ranging 
from  10,000  to  60,000,  and  as  it  is  not  advisable  to  construct 


Fig.  53. 

generators  to  develop  such  high  pressures,  raising  transformers 
are  employed  to  develop  the  line  current.  These  transformers  are 
shown  in  Fig.  53  at  a.  The  generator  develops  currents  at  1,000 
volts,  and  this  passing  through  the  primary  coils  of  the  trans- 
formers at  a  induces  secondary  currents  which  may  have  any 
voltage  desired,  say,  20,000.  These  secondary  currents  pass  to 
the  transmission  lines  b  6,  which  may  extend  a  distance  of  ten, 
twenty  or  more  miles  and  may  deliver  all  their  energy  at  the  end 
of  the  line  or  drop  part  of  it  at  intermediate  points.  The  trans- 
formers at  c  and  also  those  at  I  develop  secondary  currents  of 
any  lower  voltage  that  may  be  required  ;  thus,  those  at  c  develop 
secondary  currents  for  the  circuits  d,  which  may  be  of,  say,  1,000 
volts.  The  motor  e  is  shown  connected  directly  with  d,  but 


886  HANDBOOK   ON    ENGINEERING. 

motor  g  and  lamps  i,  k  require  a  still  lower  voltage,  hence  the 
currents  in  d  are  passed  through  a  second  set  of  transformers  at 
/,  li  and  j.  The  three  transformers  at  I  develop  secondary  cur- 
rents of  sufficiently  low  voltage  to  be  passed  through  the  rotary 
converter  m,  and  thus  provide  a  continuous  current  for  the  trolley 
road  as  shown. 

STARTING. 

When  the  armature  is  turning,  see  that  the  oil  rings  in  the 
bearings  are  in  motion.  When  the  machine  is  up  to  speed  and  all 
switches  are  open,  lower  the  brushes  on  the  commutator  and  col- 
lector, making  sure  that  each  bears  evenly  and  squarely  on  the 
surface.  Turn  the  rheostat  until  all  resistance  is  in,  then  close 
the  switch  in  the  exciter  circuit.  Set  the  exciter  brushes  properly 
and  adjust  the  voltage  of  the  exciter  to  the  proper  point. 

The  alternator  rheostat  may  then  be  turned  gradually  over  until 
the  proper  alternating  voltage  is  indicated.  The  main  circuit  of 
the  machine  may  now  be  closed.  The  commutator  brashes  should 
be  adjusted  at  a  non-sparking  position.  If  there  is  any  load  the 
voltage  should  increase  slightly.  If  it  decreases,  it  shows  that 
the  series  coils  and  the  separately  excited  coils  are  opposing  each 
other,  unless  this  decrease  is  caused  by  a  drop  in  speed.  If  it  is 
found  that  the  coils  are  opposing  each  other,  unclamp  the  brush- 
holder  yoke  of  the  alternator  and  move  its  commutator  brushes 
backward  or  forward  one  and  one-half  segments  in  a  three-phase 
machine,  and  one  segment  in  a  two-phase  machine.  A  position 
giving  maximum  voltage  will  be  found  from  which  any  motion, 
forward  or  backward,  diminishes  the  voltage.  Having  once  de- 
termined the  correct  setting  of  the  brushes,  they  may  generally 
remain  unchanged,  unless  the  generator  is  subject  to  great  varia- 
tion of  load  when  in  some  machines,  slight  movements  may  be 
found  desirable. 


HANDBOOK    ON    ENGINEERING.  887 

PARALLEL   RUNNING  OF  ALTERNATORS. 

TYPES    SUITABLE    FOR    PARALLEL   OPERATION. 

If  the  speeds  are  exactly  adjusted,  any  two  alternators  of  the 
same  frequency  will  operate  together  in  parallel.  The  maximum 
angular  displacement  that  may  take  place  between  two  machines 
in  parallel  without  causing  objectionable  phase  difference  decreases 
with  increased  number  of  poles.  For  this  reason  high  frequen- 
cies are,  generally  speaking,  less  favorable  to  parallel  operation 
than  lower  frequencies.  Machines  of  the  highest  frequencies 
ordinarily  used  can,  however,  be  successfully  run  in  parallel  if 
the  mechanical  arrangements  are  suitable. 

DIVISION    OF    LOAD. 

Machines  to  operate  in  parallel  must  run  at  such  speeds  as  will 
give  exact  equality  of  frequency.  If  the  prime  mover  running 
one  machine  tends  to  produce  a  lower  frequency  than  that  run- 
ning the  other,  the  machines  cannot  carry  equal  loads. 

When  two  alternators  operate  in  parallel,  each  must  carry  an 
amount  of  load  proportionate  to  the  power  received  from  its  prime 
mover.  If  one  engine  or  water-wheel  governs  in  such  a  manner 
as  to  give  more  power  than  the  other,  this  machine  must  carry  more 
load,  no  matter  what  the  field  excitation  may  be.  If  under  such 
conditions  the  field  excitations  are  correct,  both  machines  will  de- 
liver current  to  the  line  in  approximately  the  proportions  in  which 
they  receive  power  from  their  prime  movers.  If  the  field  adjust- 
ments are  incorrect,  there  will  be  idle  currents  between  the  machines 
in  addition  to  the  currents  which  go  to  the  line. 

COMPOUND    ALTERNATORS. 

When  compound  alternators  are  operated  in  parallel,  equalizer 
connections  should  be  used  so  that  the  rectified  alternating 


888  HANDBOOK    ON    ENGINEERING. 

current  can  properly  distribute  itself  into  the  fields  of  all  the 
machines.  Without  equalizers,  an  unstable  condition  may  exist 
which  will  render  parallel  operation  unsatisfactory.  This 
applies  particularly  in  the  case  of  machines  driven  from  the 
same  source  of  power.  The  greater  the  amount  of  compounding, 
the  greater  will  be  the  tendency  to  instability. 

BELTED    MACHINES. 

If  two  machines  are  belted  to  separate  prime  movers,  their 
parallel  operation  is  dependent  upon  the  governing  of  the  prime 
movers.  If  they  are  belted  to  the  same  source  of  power,  their 
parallel  operation  depends  upon  the  proportions  of  pulleys  and 
belts,  and  upon  the  tension  and  friction  of  the  latter.  Under 
such  conditions  the  pulleys  and  belts  must  be  adjusted  with  great 
nicety,  so  that  both  machines  will  tend,  with  proper  belt  tension, 
to  run  at  exactly  the  same  frequency.  Even  where  pulleys  are  of 
exactly  the  correct  dimensions,  a  slight  difference  in  the  thick- 
ness of  belts  may  cause  considerable  cross  currents  or  unequal 
division  of  load. 

DIRECT    COUPLED    MACHINES. 

With  such  machines,  engines  must  not  only  be  adjusted  to 
run  at  synchronous  speed,  but  must  also  be  provided  with  fly- 
wheels large  enough  to  prevent  appreciable  variations  of  fre- 
quency within  each  revolution.  Inequalities  of  speed,  due  to 
insufficient  fly-wheel  effect,  will  cause  periodic  cross  currents 
between  dynamos,  or  will  entirely  prevent  their  operation  in 
parallel.  The  greater  the  number  of  poles  in  a  direct  coupled 
machine,  the  less  the  angular  speed  variation  necessary  to  cause 
trouble. 

High  speeds  are  much  more  desirable  with  direct  coupled  alter- 
nators than  low  speeds,  and  low  frequencies  present  less  diffi- 


HANDBOOK    ON    ENGINEERING.  889 

culties  than  high.  The  desirabilty  of  high  speeds  with  direct 
coupled  alternators  cannot  be  too  strongly  stated.  While  an 
increase  of  fly  wheel  effect  will  equalize  the  angular  irregularities 
of  an  engine's  motion,  it  cannot  bring  about  such  good  results 
as  would  be  brought  about  by  a  similar  reduction  of  angular 
error  effected  through  an  increase  of  speed.  While  the  large  fly- 
wheel steadies  the  motion,  it  may  tend  to  prevent  correction  of 
the  angular  error  through  the  effect  of  the  cross  currents.  Cross 
currents  which  flow  in  machines  having  light  fly-wheels  may  have 
an  effective  tendency  to  hold  them  together ;  while  machines  with 
very  heavy  fly-wheels  may  tend  to  act  independently  of  each 
other  as  far  as  angular  variations  are  concerned. 

These  matters  should  be  carefully  considered  in  installing 
direct  connected  alternators.  Where  engines  operate  at  the  same 
speed  and  have  the  same  number  of  cranks,  this  trouble  can 
sometimes  be  overcome  by  synchronizing  the  engines  themselves  so 
that  the  impulse  in  both  come  together.  When  the  fly-wheel 
effect  is  insufficient,  the  frequency  will  fluctuate  and  this  fluctua- 
tion may  cause  serious  trouble  if  synchronous  motors  or  rotary 
converters  are  connected  to  the  circuit.  When  the  cranks  of  two 
engines  coupled  to  alternators  are  synchronized,  any  fluctuation  of 
frequency  which  is  due  to  lack  of  fly-wheel  effect  will  still  exist, 
although  it  may  not  affect  parallel  running. 

Where  alternators  have  to  be  operated  in  parallel  by  engines  to 
which  they  are  directly  coupled,  it  is  generally  desirable  to  use 
engines  having -as  many  cranks  as  possible,  so  that  the  crank 
efforts  will  be  well  distributed  throughout  the  revolution,  and 
will  not  tend  to  produce  an  irregularity  of  motion. 

STARTING. 

When  a  machine  driven  by  a  separate  engine  is  thrown  in 
parallel  with  others  which  are  carrying  load,  the  throttle  should 
be  partly  closed  so  that  it  can  just  run  at  synchronous  speed  with- 


890  HANDBOOK    ON    ENGINEERING. 

out  carrying  load.  After  it  is  in  step  with  the  other  machines, 
load  can  gradually  be  taken  on  by  giving  it  more  steam.  If  this 
is  carefully  done  the  voltage  on  the  circuit  is  not  disturbed  by  the 
addition  of  the  new  machine. 

When  a  belted  machine  is  to  be  thrown  into  parallel  with  others 
driven  by  the  same  shaft,  its  belt  tension  should  first  be  reduced, 
which  will  tend  to  admit  enough  slip  to  bring  it  into  step  with 
the  loaded  machines.  After  it  is  thrown  in  it  will  gradually  take 
load  as  the  belt  is  tightened. 

SHUTTING   DOWN. 

In  shutting  down  machines  operating  singly,  both  the  gener- 
ator and  exciter  field  resistance  should  be  cut  in  by  turning  the 
rheostat  before  the  line  switch  is  opened. 

When  two  or  more  generators  are  running  in  parallel  on  the 
bus-bars,  one  may  be  shut  down  at  any  time.  The  equalizer 
switch  should  be  opened  first,  then  the  load  reduced  by  throttling 
the  engine  or  by  slacking  the  belt.  As  soon  as  the  load  is  prac- 
tically off,  open  the  main  switch. 

CARE    OF    MACHINES. 

With  high  voltage  machines  it  is  absolutely  essential  that  they 
be  kept  scrupulously  clean.  Small  particles  of  copper  or  carbon 
dust,  may  be  sufficient  to  start  a  disastrous  arc. 

The  commutator  collector  should  receive  careful  attention  and 
be  wiped  thoroughly  every  day. 

From  time  to  time  the  machine  should  be  thoroughly  over- 
hauled and  given  a  coating  of  air-drying  japan  after  cleaning. 
Machines  of  the  rotary  field  type  are  so  constructed  that  it  is  a 
comparatively  easy  matter  to  get  at  every  part  of  the  armature 
coils.  In  a  large  station  it  is  recommended  that  an  air  compres- 
sor be  installed  so  that  a  hose  can  be  led  to  the  machine  and  the 
dust  thoroughly  blown  out. 


HANDBOOK    ON    ENGINEERING.  891 

It  is  advisable  to  have  rubber  mats  in  front  of  high  tension 
switchboards  and  on  the  floor  at  the  commutator-collector  end  of 
the  generator.  If  it  is  necessary  to  adjust  the  brushes  while  the 
machine  is  in  operation,  the  attendant  should  stand  on  the  mat 
and  it  is  also  recommended  that  he  wear  rubber  gloves. 

Both  commutator  and  collector  rings  require  a  very  slight 
amount  of  vaseline.  In  applying  it  a  dry  stick  with  a  little 
chamois  leather  tied  to  one  end  may  be  used,  so  that  there  will  be 
no  danger  of  coming  in  contact  with  the  brushes. 

With  the  brushes  properly  set  and  all  screws  firmly  tightened 
into  place,  the  generators  should  require  very  little  -attention 
while  running.  It  is  well  to  note  from  time  to  time  whether  the 
oil  rings  are  working  properly. 


ALPHABETICAL  INDEX. 


ARMATURE  cores,  23,  27. 
Armature  winding,  27,  29. 
Armature,  arrangement  of  the  field 

and,  33. 

Ammeters,  the,  60. 
Ampere,  the,  73. 
Armature,  to  remove  the,  74. 
Assembling  the  parts,  74. 
Assembly,  to  complete  the,  74. 
Armature,    effect  of  displacement 

of,  94. 

Automatic  regulator,  etc.,  108. 
Ammeter,  125. 
Arc  lamps,  125,  151. 
Arc  dynamo,  the  Thomson-Houston, 

131. 

Arc  dynamos,  installation  of,  131. 
Arc   lighting  system,    connections 

for,  133. 

Arc  dynamo,  controller  for  an,  135. 
Air  blasts  and  jets  on  L.  D.  and 

M.  D.  dynamos,  141. 
Arc  lamp,  view  of  interior  of  M., 

150. 
Arc  lamps,  connections  forM.  &K., 

152. 
Arc  lights,  repairing,  testing,  etc., 

153. 

Automatic  cut-off  engines,,  339, 
Armington  and   Sims  engine,  and 
setting  the  valves  of  same,  275. 
Automatic  lubricators,  310. 


Automatic  cut-off  engine,  card  from 
an,  350. 

Attendants,  instructions  for  boiler, 
532. 

Acids,  pumping,  579. 

Ammonia,  a  few  tests  for,  629. 

Ammonia,  effect  of  on  pipes,  631. 

Ammonia,  to  charge  the  system 
with,  632. 

Automatic  stops  for  electric  ele- 
vators, 733. 

Auxiliary  valves,  hydraulic  ele- 
vator, 775. 

Air  compressors,  losses  in,  800. 

Air  compressors,  capacity  of, 
800. 

Air  compressor,  the  McKierman, 
801. 

Air  compressor,  the  Bennett  auto- 
matic, 803. 

Air  compressor,  the  Ingersoll-Ser- 
geant,  803. 

Air  lift  system,  the  Pohle,  807. 

Alternating  current  machinery,  815. 

Alternating  currents,  the  principles 
of,  815. 

Alternating  currents,  diagrams  rep- 
resenting a  generator  of  either 
continuous  or,  817. 

Alternating  currents  and  e.m.fs., 
diagrams  showing  the  relations 
between,  821-825. 

(893) 


894 


INDEX. 


Alternating  currents,  why  they  vary 
etc.,  825. 

Alternating  current  circuits,  induc- 
tive action  in,  834. 

Angle  of  lag  between  the  current, 
etc.,  837. 

Alternating  current  generators, 
852. 

Alternating  current  generator,  dia- 
gram illustrating  a  simple,  854. 

Alternator  of  the  multipolar  type, 
855. 

Alternating  current  generators,  how 
they  are  run,  859. 

Alternators  connected  in  parallel, 
starting,  860. 

Armature,  the  effect  of  displace- 
ment of  the,  94,  98.  . 

Amperes,  per  motor,  table,  169;  170. 

Amperes,  per  lamp,  table,  173. 

Alternator  of  the  multipolar  type, 
855. 

Alternator,  a  revolving  field,  857. 

Alternator,  an  inductor,  858. 

Alternating  cu rrent  generators,  8 52 . 

Alternators  run  in  parallel,  860. 

Alternators  connected  in  parallel 
starting,  861. 

Alternators,  compensating  and  com- 

.    pounding,  864. 

Alternating  current  distributions, 
882. 

Alternators,  parallel  running  of, 
887. 

Alternators,  compound,  887. 

BRUSHES,  why  set  differently,  etc., 
36,  37. 

Brushes,  setting,  on  a  4-pole  ma- 
chine, 40. 


Brushes,  setting,  on  an  8-pole  ma- 
chine, 41. 

Building,  to  wire  a  large,  etc.,  58, 
60. 

Breakers,  circuit,  62,  63. 

Bearings,  filling  the,  74. 

Brushes,  why  they  spark,  82,  84. 

Brush  arc  lamps,  connections  for 
improved,  128. 

Brasses,  connecting  rod,  189. 

Bearings,  the  main,  190,  192. 

Boilers,  priming  in,  329,  648. 

Boiler,  the  steam,  398. 

Boilers,  energy  stored  in  steam, 
400,  401. 

Boilers,  special  high  pressure, 
401. 

Boilers,  types  of,  402. 

Boilers,  horse  power  of,  402,  404. 

Boilers,  the  rating  of,  404. 

Boilers,  working  capacity  of,  405, 
406. 

Boiler  tests,  code  of  rules  for  mak- 
ing, 407,  414. 

Boilers,  and  boiler  material,  defi- 
nitions as  applied  to,  415. 

Boiler,  selection  of  a,  422,  425. 

Boiler  trimmings,  426,  432. 

Boiler,  care  and  management  of  a, 
433,  437. 

Boilers,  water  for  use  in,  438,  448. 

Boiler,  use  and  abuse  of  the  steam, 
449,  453. 

Boilers,  design  of  steam,  454,  455. 

Boilers,  forms  of  steam,  456. 

Boilers,  setting  steam,  456,  457. 

Boilers,  defects  in  the  construction 
of  steam,  457,  459. 

Boilers,  improvements  in  steam, 
'459,  461. 


INDEX. 


895 


Boiler  surfaces,  strength  01  stayed 
flat,  473. 

Boiler  stays,  474,  477. 

Boilers,  pulsation  in  steam,  487. 

Boilers,  water  columns  for,  489. 

Boiler,  the    water-tube    sectional, 
502. 

Boiler  setting  and  furnace,  view  of, 
513. 

Boilers,  vertical  tubular,  514,  521. 

Boilers,  table  of  pressures,  allow- 
able in,  516. 

Boiler  settings,  fire  line  in,  520. 

Boiler  setting,  number    of  bricks 
required  for,  522. 

Boiler,   specifications  for  a  sixty- 
inch  6-inch  fiue,  524. 

Banking  fires,  531. 

Boiler  attendants,  instructions  for, 
532. 

Boilers,  rules  and  problems  anent 
steam,  536. 

Blake  steam  pump,  the,  555. 

Blake  pump,  operation  of  the,  556. 

Boiler  for  a  steam  pump,  selecting, 
580. 

Brine  system,  622. 

Brine,  the  preparation  of,  624. 

Buildings,  insulation  of,  626. 

Boilers,  foaming  in,  648. 
Boiler,  in  case  of  low  water  in  a 
649. 

Boilers,  rating  by  feed  water,  676 

Bevel  wheels,  707. 

Belt  driven  elevators,  716,  725. 

Brake,  the  elevator  machine,  720. 

Brake  magnet,  the  safety,  739. 

Belts  and  how  to  care  for  them,  786. 

Belts,  the  driving  power  of,  788. 

Belting,  strain  or  tension    on,  788. 


Belting,  rules  and  problem  sanent, 

788,  797. 
Belts,    extracts  from  articles  on, 

790. 

Belts,  transmitting  power  of,  795. 
Belts,  table  of  horse-power  of,  796, 

799. 
Belting,  directions  for   adjusting, 

798. 
Bennett  automatic  air  compressor, 

803. 

CORES,  the  armature,  23,  27. 

Circuits,  distributing,  47. 

Constant  potential,  generators  of 
the,  47,  48. 

Circuit  breakers,  62,  63. 

Current,  the  strength  of  an  elec- 
tric, 73. 

Candle  power,  73. 

Commutator,  care  of,  75. 

Commutator  gives  trouble,  if  the,  76. 

Commutator  brushes,  why  they 
spark,  82,  84. 

Current,  the  way  it  is  shifted,  84, 
85. 

Commutated  coil,  etc.,  if  the,  86. 

Controller,  diagram  showing  con- 
nections of  Brush,  118. 

Controller  for  arc  dynamo,  view  of, 
135. 

Commutator  segments  and  brush 
holders,  138. 

Cut-off  in  parts  of  the  stroke,  table 
of,  183. 

Crank-pins,  188.  ' 

Connecting  rod  brasses,  189. 

Centers,  to  find  the  dead,  195. 

Compound  engine,  view  of  tandem, 
198. 


896 


INDEX. 


Compound    engine,   the    Westing- 
house,  293. 

Cylinder  lubrication,  309. 
Cut-off,  view  of  a  slide  valve  engine 

showing  point  of,  321. 
Compression  begins,  view  showing 

the  position  of  slide  valve,  when, 

321,  322. 
Card    from    a    throttling    engine, 

347. 
Card    from  an    automatic  cut-off 

engine,  350. 
Calculating  mean  effective  pressure, 

351. 

Curve,  the  theoretical,  353,  357. 
Card  from  a  Corliss  engine,  357. 
Card,  a  stroke,  358. 
Card,  a  steam  chest,  359. 
Cards,  eccentric  out  of  place,  360, 

361. 

Cards,  eccentric,  361,  365. 
Cards  from  "  Eclipse  "  ice  machine 

plant,  371,  373. 
Corliss  engine,  how  to  increase  the 

power  of  a,  381,  382. 
Code  of  rules  for  making  boiler 

tests,  407,  414. 
Centrifugal  force,  501. 
Cocks,  proper  location  of  gauge, 

521. 
Compound  pump,  the  Worthington, 

544. 

Cameron  steam  pump,  the,  548. 
Corrosion  in  water  pipes,  579. 
Condenser,  function  of  the  pump 
,    and,  621. 
Cold,  mechanical,  easily  regulated, 

622. 

Cold,  utilizing  the,  622. 
Capacity,  unit  of,  624. 


Compressor,  view  of  the  "  Eclipse,' 

635. 

Compressor  pumps,  636. 
Compressor,  view  of  double  acting, 

640,  644. 

Chimneys,  688,  794. 
Chordal  pitch,  to  find  the,  699,  703. 
Curves  of  teeth,  705. 
Circuit  connections,  view   of,  734. 
Coils,  cutting  out  the   series  field, 

737. 

Car,  how  to  start  the,  743. 
Car  switch,  the,  748. 
Cable  switch,  the  slack,  749. 
Cables  and  how  to  care  for  them, 

783. 
Cylinder,  contents  of  same  in  cubic 

feet  for  each  foot  in  length,  801. 
Compressor,  the  McKierman    air, 

801. 

Compressor,    The     Bennett    auto- 
matic air,  803. 
Compressor,     The      Ingersoll-Ser- 

geant  Air,  803. 
Current     machinery,     alternating, 

815. 

Currents,  the  principles  of  alternat- 
ing, 815. 
Currents,  diagrams  representing  a 

generator  of  either  continuous  or 

alternating,  817. 
Currents    and    e.m.fs.,     diagrams 

showing  the    relations   between 

alternating,  821,  825. 
Currents  vary,  etc.,  one  reason  why 

alternating,  825. 
Curves    are  used,    etc.,   diagrams 

showing  the  way  in  which  sine, 

826. 
Currents,  polyphase,  832. 


INDEX. 


897 


Currents,  etc.,  unbalanced  three- 
phase,  834. 

Current  circuits,  etc.,  inductive 
action  in  alternating,  834. 

Current,  etc.,  the  angle  of  lag  be- 
tween the,  837. 

Condensers,  etc.,  by  the  use  of,  840. 

Condensers,  etc.,  the  general  prin- 
ciple of  construction  of  a,  841. 

Current  generator,  diagram  illus- 
trating a  simple  alternating,  854. 

Current  generators  are  run,  how 
alternating,  859. 

Currents,  field  magnetizing,  867. 

Converters,  rotary,  878. 

DYNAMOS,  general    directions  for 

starting,  76,  77. 

Dynamos  to  full  speed,  bringing,  77. 
Dynamo  with  another,  connecting 

one,  78. 

Dynamos  into  circuit,  switching,  78. 
Dynamos,  how  connected  together, 

78. 

Dynamos  in  parallel,  79. 
Dynamos    and  motors,  directions 

for  running,  80. 
Dynamos,  precautions  in  running, 

81. 
Dynamo    or  motor,  heating   in  a, 

93,  94. 

Dynamo,  view    of  the    Thomson- 
Houston  standard  arc,  131. 
Dynamos,  installation  of  arc,  131. 
Dynamo,  view  of  controller  for  an 

arc,  135. 
Dynamos,   diagrams  showing  best 

position  of  air  blasts  and  jets  on 

L  D  and  M  D,  141. 
Dead  centers,  to  find  the,  195. 


Down  draft  furnace,  the,  503,  522. 
Deane  steam  pump,  the,  546. 
Duplex  pump,  how  to  set  the  steam 

valves  of  a,  567. 
Decimal  equivalents  of  16ths,  32ds, 

and  64ths,  of  an  inch,  table  of, 

583. 
Decimal  equivalents  of  one  foot  by 

inches,  714. 
Decimal  equivalents  of  an  inch,  787. 

ELECTRICAL  MACHINERY,  the  ele- 
mentary principles  of,  1. 

Electromagnetic  induction,  the 
principles  of,  14,  22. 

Electromotive  in  volts,  force,  etc., 
the,  63. 

Electric  motors,  64. 

Electric  light  conductors  table, 
176. 

Electric  current,  etc.,  the  strength 
of  an,  73. 

Engine,  the  steam,  177. 

Engine,  the  selection  of  an,  177. 

Expansion,  the  gain  by,  183. 

Engine,  care  and  management  of  a 
steam,  185. 

Engine,  lubrication  of  an,  186. 

Engine,  selecting  an  oil  for  an,  187. 

Engines,  knocking  in,  189  to  190. 

Engines,  repairs  of,  191. 

Eccentric  straps,  192. 

Engines,  automatic,  194. 

Engine,  view  of  a  tandem  com- 
pound and  its  foundation,  198. 

Engine,  how  to  line  an,  199,  203. 

Engine,  view  of  a  twin  tandem 
compound;  showing  a rrangemem 
of  piping,  200. 

Engine,  horse  power  of  an,  252. 


898 


INDEX. 


Engines,  general  proportions  of, 
252. 

Engine,  view  of  the  Kussell,  254. 

Engine,  setting  the  valves  of  a 
Russell,  254. 

Engine,  view  of  Porter- Allen,  258. 

Engine,  description  of  the  Porter- 
Allen,  259,  271. 

Engine,  directions  for  setting  the 
valves  and  running  Porter-Allen, 
271,273. 

Engine,  the  Armington  and  Sims, 
275. 

Engine,  the  Harrisburg,  276. 

Engine,  the  Mclntosh  and  Sey- 
mour, 281. 

Engine,  the  Ideal,  283. 

Engine,  the  Westinghouse  com- 
pound, 293. 

Engine,  view  of  a  slide  valve 
(showing point  of  taking  steam), 
321. 

Engin  ,  view  of  a  slide  valve 
(showing  the  point  of  cut-off), 
321. 

Engines,  condensing,  232. 

Engines,  slide  valve,  337. 

Engines,  regular  expansion,  338. 

Engines,  automatic  cut-off,  339, 
340. 

Engines,  the  difference  in  the  action 
of  throttling  and  automatic  en- 
gines, 375,  379. 

Engines,  economy  of  steam,  380. 

Engine,  how  to  increase  the  power 
of  a  Corliss,  381,  382. 

Engine,  how  to  increase  the  power 
of  a  throttling,  383. 

Engine,  how  to  increase  the  power 
of  a  shaft  governor,  385. 


Engine,  how  to  line  an  (with  a 
shaft  placed  at  a  higher  or  a 
lower  level),  385,  387. 

Engine,  how  to  line  an  (with  a 
shaft  to  which  it  is  to  be  coupled 
direct,  387. 

Engine,  rules  and  problems  apper- 
taining to  the  steam,  392,  395. 

Engine,  to  find  the  water  consump- 
tion of  a  steam,  395,  397. 

Engine,  best  economy  in  running 
an,  650. 

Expansion  of  steam,  654. 

Engine,  taking  up  lost  motion  m 
an,  654. 

Engines,  feed  water  required  for 
small,  676. 

Electric  elevators,  716. 

Elevators,  electric,  716. 

Elevator,  the  Otis,  716. 

Elevators,  belt  driven,  716,  725. 

Elevators,  direct  connected,  717, 
730. 

Elevator  machine  brake,  the,  720. 

Elevator,  view  of  connections  of 
gravity  motor  controller  to,  722. 

Elevators,  electric  control,  for  pri- 
vate house,  749. 

Elevators,  the  Sprague  Electric 
Co.'s,  756. 

Elevator,  view  of  operative  circuits 
for  Sprague  screw,  762. 

Elevators,  care  of  Sprague,  765. 

Elevators,  directions  for  the  care 
and  operation  of  electric,  765. 

Elevators,  hydraulic,  769. 

Elevators,  how  to  pack  hydraulic 
vertical  cylinder,  769. 

Elevator,  view  of  Otis  vertical  hy- 
draulic, 772.  > 


IttDEX. 


899 


Elevators,  care  of  Hale,  777. 

Elevators,  water  for  use  in  hy- 
draulic, 778,  781. 

Elevator  inclosures  and  their  care, 
782. 

Elevators,  lubrication  for  hydraulic, 
785. 

FORCE,  magnetic  lines  of,  6. 

Force,  lines  of,  0,  14. 

Force,  magnetic,  13. 

Field  and   armature  in  a  two-pole 

machine,    general     arrangement 

of,  33,  36. 
Fly-wheel,  the,  184. 
Fly-wheels,  rules  for  weights   of, 

253. 
Flues,    riveted    and    lap    welded, 

477. 
Flues,  table    of    allowable    steam 

pressure  on,  478. 
Force,  centrifugal,  501. 
Furnace,  the  down  draft,  503. 
Fire-line  in  boiler  settings,  520. 
Fires,  banking,  531. 
Friction  of  water  in  pipes,  loss  by, 

588. 

Foaming  in  boilers,  G48. 
Feed-water  required  for  small  en- 

gines,  G76. 

Feed-water,  heating,  070. 
Feed-water,  rating  boilers  by,  070. 
Feed-water  and  steam,  weights  of, 

077. 

Feed-water  heaters,  678. 
Feed-water  heaters,  gain  by  use  of, 

680. 
Field  coils,  cutting  out  the  series, 

737. 
Fluid,  soldering,  101. 


GENERATORS  and  motors,  two-pole, 
27,  30. 

Generators  of  the  constant  poten- 
tial, 47,  48. 

Generators  of  the  shunt  type,  the 
switch  board  arranged  for  two, 
49. 

Generators  and«motors,  instructions 
for  installing  and  operating  slow 
and  moderate  speed,  74. 

Governor,  the  steam  engine,  183- 
194. 

Governor,  specifications  for  cen- 
trally balanced  centrifugal  iner- 
tia, 273. 

Governor,  the  Gardiner  spring,  341. 

Governor,  the  Gardiner  standard, 
342. 

Gauges,  steam,  489. 

Gauge-cocks,  proper  location  of, 
521. 

Gears,  horse  power  of,  695. 

Gearing,  wheel,  698. 

Gear-wheel,  pitch  line  of  a,  698. 

Gear-teeth,  stress  orr,  705. 

Gearing,  construction  of,  706. 

Gears,  calculating  the  speed  of,  710. 

Gauges,  wire,  175. 

HORSE-POWER,  185,  238. 
Harrisburg  engine,  the,  276. 
Hyperbolic  logarithms,  table  of,  397. 
Heat  and  steam,  410. 
Heating  surface  in  square  feet,  table 

of,  501. 

Hooker  steam  pump,  the,  553. 
Hancock  inspirator,  directions  for 

connecting  and  operatingthe,  597. 
Heating  feed-water,  676. 
Heaters,  feed-water^  678. 


900 


INDEX. 


Heat,  units  of,  required  to  convert 
one  pound  of  water,  etc.,  679. 

Horse-power  of  gears,  695. 

Horse-power  of  shafts,  697. 

Hydraulic  elevators,  769. 

Hydraulic  vertical  cylinder  eleva- 
tors, how  to  pack,  769. 

Hydraulic  elevators,  water  for  use 
in,  778. 

Hydraulic  elevators,  lubrication 
for,  785. 

IDEAL  engine,  the,  283. 

Indicator,  a  few  remarks  on  the, 
345. 

Indicator,  the  use  of,  in  setting 
valves,  346. 

Iron  per  lineal  foot,  weight  of 
square  and  round,  488. 

Instructions  for  boiler  attendants, 
532. 

Ignition  points  of  various  sub- 
stances, 589. 

Injector  and  inspirator,  the,  591. 

Injector,  the  first  appearance  of  the, 
592. 

Injectors,  general  directions  for 
piping,  594. 

Injectors,  care  and  management  of, 
599. 

Inspirator,  directions  for  connect- 
ing and  operating,  597. 

Insulation  of  buildings,  626. 

Insulation,  perfect,  628. 

Iron,  table  of  weight  of  a  square 
foot  of  sheet,  712. 

Ingersoll-Sergeant  air  compressor, 
the,  803. 

Inductive  action  in  alternating  cur- 
rent circuits,  etc.,  834. 


Induction,  mutual,  842. 
Ice-making  plant,  a  complete,  639, 

640. 
Incandescent  wiring  tables,  160  to 

168. 
Insulation  resistance,  100. 

JOURNALS,  heating  of,  193. 
Joints,  maximum  pitches  for  riveted 

lap,  466. 

Joints,  double  riveted  lap,  467. 
Joints,  single  riveted  lap,  46<). 

KNOCKING  in  engines,  189. 
Knowles,  steam  pump,  the,  550. 

LINES  of  force,  magnetic,  6. 

Lines  of  force,  6,  14. 

Lamps,  connections  for  improved 
brush  arc,  128. 

Lighting  system,  diagram  of  con- 
nections for  arc,  133. 

Leads,  table  of,  140. 

Lamps,  instructions  for  the  instal- 
lation and  care  of  arc,  151. 

Lamp,  view  of  interior  of  M  arc,  150. 

Lamps,  starting  the,  152. 

Lamps,  diagram  of  connections  for 
M  and  K  arc,  152. 

Lights,  instructions  for  repairing, 
testing,  and  adjusting  arc,  153. 

Lubrication  of  an  engine,  186. 

Lubricators,  automatic,  310. 

Link  motion,  setting  a  plain  slide 
valve  with,  313. 

Lining  an  engine  with  a  shaft  placed 
at  a  higher-or  lower  level,  385. 

Lining  an  engine  with  a  shaft  to 
which  it  is  to  be  coupled  direct, 
387. 


INDEX. 


901 


Logarithms,   table   of    hyperbolic, 

397. 
Lap  joints,  maximum   pitches   for 

riveted,  466. 

Lap  joints,,  double  riveted,  467. 
Lap  joints,  single  riveted,  469. 
Lubrication   of    refrigerating    ma- 
chinery, 630. 
License,  some   practical  questions 

usually  asked  of  engineers  when 

applying  for,  646. 
Lead,  what  is  valve,  653,  666,  668. 
Lap  on  a  valve,  what  Is,  654,  666, 

670. 
Lost  motion  in   an  engine,  taking 

up,  654. 
Line  shaft,  instructions   for  lining 

up  extension  to,  672. 
Lamps  are  connected,  the  way  in 

which  synchronizing,  863. 
Load,  division  of,  887. 

MAGNET,  a  permanent,  1  to  2. 

Magnet,  two-bar,  3  to  6. 

Magnet  needle,  a,  3. 

Magnetic  lines  of  force,  6. 

Magnetic  force,  13. 

Magnet,  to  find  the  lifting  capacity 

of  a,  13. 
Motors,  two-pole    generators  and, 

27. 

Multipolar  machines,  38,  39. 
Motors,  electric,  64. 
Motors  and  their  connections,  64, 

73. 
Motors,  instructions  for  installing 

and  operating  slow  and  moderate 

speed  generators  and,  74. 
Motors,    directions     for     running 

dynamos  aud,  80, 


Meter  for  station  use,  view  of,  149. 
Meters,  Watt,  150,,  151. 
Main  bearings,  the,  190. 
Mclntosh  and  Seymour  engine,  281. 
Mclntosh  aud  Seymour  engine,  how 

to  set  the  valves  of  a,  281. 
Miscellaneous  pump  questions  and 

answers,  559,  603. 
Meter,  the  Worthington  water,  581. 
Machines  for  ice  making,   rating, 

638. 

Metals,  melting  points  of,  687. 
Manila  rope,  transmission  of  power 

by,  714,  812,  813. 

Motor  controller,  view  of  connec- 
tions of  gravity,  723. 
Magnet,  the  safety  br-ake,  739. 
Machines,  the  proper  care  of,  739, 

779. 

Motor,  the  pilot,  763. 
Metric  system,  the,  809. 
McKiermau  air  compressor,  801. 
Mutual  induction,  842. 
Motors,  induction  and  other  types 

of,  871. 
Motor,  principle  of  the  induction, 

872,  877. 
Motors,  three-phase  induction,  877, 

878. 

Machines,  belted,  888. 
Machines,  direct  coupled,  888. 
Machines,  care  of,  890. 

NEEDLE,  a  magnet,  3. 
Noise  in  dynamos,  91,  92. 

OTIS  elevator,  the,  716. 

Otis  vertical  hydraulic  elevator  and 

valve  chamber,  view  of,  772. 
Otis  gravity  wedge  safety,  777. 


902 


INDEX. 


PRECAUTIONS  in  running  dynamos, 
81. 

Personal  safety,  81. 

Polarity,  reversal  of,  142. 

Plug  switchboard,  standard  for  6 
circuits,  148. 

Piston  packing,  187. 

Pins,  crank,  188. 

Piping,  arrangement  of,  etc.,  200. 

Power,  what  is,  251. 

Porter-Allen  engine,  view  and  de- 
scription of  the,  258 j  273. 

Power  plant,  taking  charge  of  a 
steam,  323. 

.Priming  in  boilers,  329. 

Pipes,  loss  of  heat  from  uncovered 
steam,  391. 

Pressure  allowable  on  flues,  478. 

Pipe,  table  of  wrought-iron  welded, 
486. 

Pressures  allowable  in  boilers, 
table  of,  510. 

Pump,  the  steam,  544. 

Pump,  the  Worthington  compound, 
544. 

Pump,  the  Deane  steam,  54G. 

Pump,  the  Cameron  steam,  548. 

Pump,  the  Knowles  steam,  550. 

Pump,  the  Hooker  steam,  553. 

Pump,  the  Blake  steam,  555. 

Pump  questions  and  answers,  mis- 
cellaneous, 559,  503. 

Pump,  how  to  set  the  valves  of  a 
duplex,  567. 

Pipe  connections,  proper,  569. 

Pipe  connections,  view  of,  570. 

Pumps  refusing  to  lift  water, 
577. 

Pipes,  corrosion  in  water,  579. 

Pumping  acids,  579. 


Pump,   selecting    a    boiler    for     a 

steam,  580. 

Pipes,  loss  by  friction  in  water,  588. 
Pump  and  condenser,  function  of, 

621. 

Pumps,  compressor,  036. 
Pipe  arrangement  for  vaults,  037. 
Practical  questions   usually  asked, 

etc.,  640. 
Pumps  do  not  work,  reasons   why, 

647. 

Priming  in  boilers,  048. 
Piping,  simplicity  in  steam,  074. 
Pipe  to  order,  cutting,  075. 
Pure  water,  081. 
Prime  movers,  097. 
Pitch  line  of  a  gear  wheel,  698. 
Pitch,  to  tind  the  chorda!,  699,  703. 
Pinion,   to    find    the     proportional 

radius  of  a  wheel  or,  700. 
Pinion,  to  find  the  diameter  of  a,700. 
Pinion,  to  find  the  number  of  revo- 
lutions of  a  wheel  or,  700,  701. 
Pinions,  a  train  of  wheels  and,  701. 
Pitches  of  wheels,  table  of,  704. 
Pilot  motor,  the,  703. 
Pressure  tanks,  to  find  leaks  in,  786. 
Pohle  air  lift  system,  the,  807. 
Polyphase  currents,  832. 
Piston,  to  test  a   (for  leakage  of 

steam,  669. 
Power  factor,  870. 

REGULATORS  for  Brush  arc  genera- 
tors, 120  to  125. 

Rod  brasses,  connecting,  189. 

Repairs  of  engines,  191. 

Rules  for  weights  of  fly-wheels,  253. 

Russell  engine,  view  of  the,  240, 
254. 


INDEX. 


903 


Regular  expansion  engines,  338. 

Rules  and  problems  appertaining  to 
the  steam  engine,  31)2,  395. 

Riveted  seams,  strength  of,  461, 466. 

Riveted      lap      joints,      max  murn 
pitches    for,  466,  469. 

Rules    and  problems   anent   steam 
boilers,  536. 

Rules     and    problems     anent    the 
steam  pump,  603,  617. 

Refrigeration,  mechanical,  619. 

Rating   of     ice   machines   in    tons 
capacity,  623. 

Ratings,  difference  in  the,  623. 

Refrigerating    machinery,    lubrica- 
tion of,  630. 

Refrigeration,   process  of  mechan- 
ical, 633. 

Rating  machines   for   ice   making,  j 
638. 

Refrigerating    plant,    a    complete, 
642. 

Reasons  why  pumps  do  not  work, 
647. 

Rating  boilers  by  feed  water,  676. 

Rope,  the  main  hand,  721. 

Resistance,  the  starting,  735. 

Rope,  standard  hoisting,  783. 

Rules  and  problems  anent  belting, 
788,  797. 

Rope  transmission,  714,  812,  813. 

Ropes,  horse  power  transmitted  by 
hemp,  813. 

Ropes,  to  test  the  purity  of  hemp, 
814. 

Rope  data,  wire,  814. 

Rheostat,  diagram  of,  connections 
for,  134. 

Rotary  transformers  and  convert- 
ers, 878. 


Rotary    transformer,    principle   of 

the,  879. 

SWITCH  boards,  76. 

Starting  the  generator,  76. 

Sparking,  87,  91. 

Switchboard  for  6  circuits,  147. 

Switchboard,    view    of     back    of, 

148. 

Starting  the  lamps,  152. 
Steam    engine,   care   and   manage- 
ment of  the,  185. 

Selecting  an  oil  for  an  engine,  187. 
Straps,  eccentric,  192. 
Steam  power  plant,  taking  charge 

of  a,  323. 
Steam  power  plants,  economy   in, 

327,  329. 

Steam,  high  pressure,  332,  335. 
Steam,  using  same  full  stroke,  335, 

337. 

Slide  valve  engines,  337. 
Steam  engines,  economy  of,  380. 
Slide  valve,  how  to  set  in  a  hurry, 

388. 

Slide  valve,  the  travel  of  a,  390. 
Steam  pipes,   loss    of    heat    from 

uncovered,  391. 
Steam,  heat  and,  416,  421. 
Seams,   strength   of    riveted,    461, 

466. 
Stayed  flat  boiler  surfaces,  strength 

of,  473. 

Stays,  boiler,  474,  477. 
Steam  gauges,  489,  490. 
Safety  valves,  491,  499. 
Safety  valve  rules,  497. 
Steam  jets  for  smoke   prevention, 

542. 
Smoke  prevention,  542. 


904 


INDEX. 


Substances,  ignition  points  of  vari- 
ous, 589. 

Steam,  expansion  of,  654. 

Steam,  weights  of  feed  water  and, 
677. 

Steam,  the  temperature  and  pres- 
sure of  saturated,  684. 

Something  for  nothing,  686. 

Stacks,  weight  of  steel  smoke  (per 
lineal  foot),  694. 

Shafts,  table  of  the  horse  power  of, 
697. 

Stress  on  gear  teeth,  705. 

Screw,  the  worm,  708. 

Sheet-iron,  table  of  weight  of  a 
square  foot  of,  712. 

Screw-cutting,  713. 

Switch,  the  motor  starting,  719. 

Stops,  automatic,  733. 

Switch  lever,  the  736. 

Switch,  the  car,  748. 

Switch,  the  slack  cable,  749. 

Sprague  Electric  Co.'s  elevators, 
756. 

Sprague  screw  elevator,  view  of 
operative  circuits  for,  762. 

Sprague  elevators,  care  of,  765. 

Steam,  the  force  of,  etc.,  398,  400. 

Starting  direct  coupled  machines, 
886,  889. 

Shutting  down,  890. 

Soldering  fluid,  101. 

TWO-BAR  magnet,  3,  6. 

Two-pole  generators   and  motors, 

27,  30. 
Thomson-Houston     standard     arc 

dynamo  arranged  for  right  hand 

rotation,  view  of,  131. 
Table  of  leads,  140. 


Table  of  cut-off  in  parts  of  the 
stroke,  183. 

Fitting  a  slide  valve,  191. 

Theoretical  curve,  the,  353,  357. 

Throttling  and  automatic  engines, 
374,  379. 

Travel  of  a  slide  valve,  390. 

Types  of  boilers,  402. 

Trimmings,,  boiler,  426, 432. 

Table  of  allowable  steam  pressure 
on  flues,  478,  479. 

Tubes,  thickness  of  material  re- 
quired for,  481,  486. 

Table  of  the  rise  of  safety  valves, 
494. 

Table  of  heating  surface  in  sq.  ft. 
501. 

Table  of  water  pressure  due  to 
height,  582. 

Tanks,  capacity  of,  in  U.  S.  gal- 
lons, 584. 

Testing  for  water  in  ammonia,  629. 

Taking  up  lost  motion  in  an  engine, 
654. 

Table  showing  the  units  of  heal 
required  to  convert  one  pound  of 
water  at  the  temperature  of  32° 
F.  into  steam  at  different  pres- 
sures, 679. 

Table  showing  the  gain  by  the  use 
of  feed  water  heaters,  etc.,  680. 

Temperature,  and  pressure  of  sat- 
urated steam,  the,  684. 

Table  of  diameters  and  pitches  of 
wheels,  704. 

Teeth,  curves  of,  705. 

Teeth  of  wheels,  proportions  of, 
709. 

Tooth,  to  find  the  depth  of  a  cast 
iron,  709. 


INDEX. 


905 


Tooth,  to  find  the  H.  P.  of  a,  710. 

Transmission  of  power  by  manila 
rope,  714,  812,  813. 

Table  of  transmission  of  power  by 
wire  ropes,  715,  814. 

Tanks,  to  find  the  leaks  in,  pres- 
sure, 786. 

Transmitting  power  of  belts,  795. 

Table  of  horse  power  of  belts,  796, 
799. 

Thermometers,  811. 

Transformers,  844. 

Transformer,  the  action  in  a,  846. 

Transformers,  the  object  in  using, 
849. 

Tables,  incandescent  wiring,  160  to 
168. 

Table  of  amperes  per  motor,  169, 
170. 

Table  of  volts  lost  at  different  per 
cent  drop,  171,  172. 

Table  of  amperes  per  lamp,  173. 

Table  of  copper  wire,  174. 

Table  of  wire  gauges,  175. 

Table  of  electric  light  conductors, 
176. 

Table  of  carrying  capacity  of  wires, 
99,  101. 

Table  of  properties  of  water  be- 
tween 32°  and  212°  Fall.,  679. 

UNBALANCED  three-phase  currents, 

etc.,  834. 
Useful  information,  786. 

VALVE,  fitting  a  slide,  191. 

Valve  setting  for  engineers,   318, 

322. 

Valve,  the  travel  of  a  slide,  390. 
Valves,  safety,  491,  499. 


Valve  lead,  what  is,  653,  666,  668. 

Valve  gear,  describe  the  Corliss 
engine,  654. 

Valve,  what  is  lap  on  a,  654,  666, 
670. 

Valve  motion,  direct  and  indirect, 
668. 

Valves,  how  to  pack  vertical  hy- 
draulic elevator  cylinder,  771. 

Volts  lost  at  different  per  cent 
drop,  171,  172. 

WATT,  the,  73. 

Watt  meters,  connections  for,  etc., 

149. 

Watt  meters,  150. 
Work,  what  is,  251. 
Westinghouse    engine,     the,     293, 

301. 
Water  consumption  of  an  engine, 

to  find  the,  395. 

Water  columns  for  boilers,  489. 
Water  column  connections,  proper, 

515. 
Worthington     water    meter,    the, 

581. 

Water,  weight  of,  585. 
Water,  cost  of,  587. 
Water  may  be  wasted,  how,  589. 
Wheel,  to  find  the  diameter  of  a, 

699. 
Wheel,  to  find  the  number  of  teeth 

for  a,  699. 
Wheel,  to  find  the  circumference 

of  a,  700. 

Wheels,  bevel,  707. 
Worm  screw,  708. 
Wiring  for  private  houses,  view  of, 

750. 
Wiring  tables,  160  to  168. 


906 


INDEX. 


Wire,     approximate      weight      of     Wires,  table  of  carrying  capacity 


"  O.  K."  triple  braided  weather 
proof  copper,  174. 
Wire  gauges,  difference  between, 
175. 


of,  99,  101. 

Water,    table    of     properties     of 
water,  etc.,  002. 

ZIGZAG  riveting  and    chain  rivet- 
ing, 408,  472. 


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